This reverts commit f5ac225c, i.e. https://github.com/flutter/flutter/pull/137115.

This is a continuation of https://github.com/flutter/flutter/pull/142266 that was redone based on feedback to make this easier to revert in the future. The exact steps I took to create this revert:

1. Revert commit noted above
2. Fix merge conflicts, that notably involved reverting some changes in https://github.com/flutter/flutter/pull/140744 ~and https://github.com/flutter/flutter/pull/141417~ (fixed my merge to avoid the second PR from being affected)
3. Delete `packages/flutter_tools/test/integration.shard/android_plugin_skip_unsupported_test.dart` as this was added in the commit noted above

cc @Gustl22 since I couldn't tag as a reviewer

This PR increases Android's `minSdkVersion` to 21.

There are two changes in this PR aside from simply increasing the number
from 19 to 21 everywhere.

First, tests using `flutter_gallery` fail without updating the
lockfiles. The changes in the PR are the results of running
`dev/tools/bin/generate_gradle_lockfiles.dart` on that app.

Second, from
[here](https://developer.android.com/build/multidex#mdex-pre-l):
> if your minSdkVersion is 21 or higher, multidex is enabled by default
and you don't need the multidex library.

As a result, the `multidex` option everywhere is obsolete. This PR
removes all logic and tests related to that option that I could find.
`Google testing` and `customer_tests` pass on this PR, so it seems like
this won't be too breaking if it is at all. If needed I'll give this
some time to bake in the framework before landing the flutter/engine
PRs.

Context: https://github.com/flutter/flutter/issues/138117,
https://github.com/flutter/flutter/issues/141277, b/319373605

This PR adds a test that reproduces the problem described in the linked issue: hot restart on the web seems to not update if the app being run is `const`.

The new test is expected to fail, until the `const` issue with hot restart in the web is resolved.

Expected failure mode is a 15s timeout in the following test:

```
02:31 +3 ~1 -1: Hot reload (index.html: Default) (with `const MyApp()`)): newly added code executes during hot restart [E]
  TimeoutException after 0:00:15.000000: Future not completed
  dart:async  _startMicrotaskLoop
  ...
```

(And then a bunch of output that I'm not 100% sure is intended :))

## Issues

* #141588

Add an option to use named argument for generated method.

Fix #116308

Relands #97823

When the tool migrated to `.flutter-plugins-dependencies`, the Gradle plugin was never changed.
Until now, the plugin had the heuristic that a plugin with a `android/build.gradle` file supported the Android platform.

Also applies schema of `getPluginDependencies` to `getPluginList` which uses a `List` of Object instead of `Properties`.

Fixes #97729
Cause of the error: https://github.com/flutter/flutter/blob/5f105a6ca7a5ac7b8bc9b241f4c2d86f4188cf5c/packages/flutter_tools/gradle/flutter.gradle#L421C25-L421C25

Fixes #98048
The deprecated line `include ":$name"` in `settings.gradle` (pluginEach) in old projects causes the `project.rootProject.findProject` to also find the plugin "project", so it is not failing on the `afterEvaluate` method. But the plugin shouldn't be included in the first place as it fails with `Could not find method implementation() for arguments` error in special cases.

Related to #48918, see [_writeFlutterPluginsListLegacy](https://github.com/flutter/flutter/blob/27bc1cf61a5b54bf655062be63050123abb617e4/packages/flutter_tools/lib/src/flutter_plugins.dart#L248).
Co-authored-by: Emmanuel Garcia <egarciad@google.com>

Update Android SDK from 33 to 34.

Following the engine update:

* https://github.com/flutter/engine/pull/47839

Work in progress... currently testing against presubmit.

Re-lands https://github.com/flutter/flutter/pull/137191.

The fix for the issue causing that PR to be reverted was tested in this PR but ultimately landed separately in https://github.com/flutter/flutter/pull/138093.

Reverts flutter/flutter#137191
Initiated by: camsim99
This change reverts the following previous change:
Original Description:
Adds support for Android 34 in the following ways:

- Bumps integration tests compile SDK versions 33 --> 34
- Bumps template compile SDK version 33 --> 34
- Also changes deprecated `compileSdkVersion` to `compileSdk`

Part of https://github.com/flutter/flutter/issues/134220

Adds support for Android 34 in the following ways:

- Bumps integration tests compile SDK versions 33 --> 34
- Bumps template compile SDK version 33 --> 34
- Also changes deprecated `compileSdkVersion` to `compileSdk`

Part of https://github.com/flutter/flutter/issues/134220

I'm seeing these in the bot reports every week. Hopefully this is all of
them, and hopefully 4GB is enough.

New feature in upcoming Dart 3.2. See https://github.com/dart-lang/language/issues/2020. Feature is enabled by bumping the min SDK version to 3.2.

Part of https://github.com/flutter/flutter/issues/134476.

Fixes https://github.com/flutter/flutter/issues/132157

Partially fixes/related to: https://github.com/flutter/flutter/issues/131425

Deletes deprecated splash screen meta-data element.

This is no longer needed to present a splash screen in a Flutter application, but will be removed soon. See [go/flutter-splash-screen-migration](http://go/flutter-splash-screen-migration) for more information.

Part of https://github.com/flutter/flutter/issues/105173.

Based on the [message format
syntax](https://unicode-org.github.io/icu/userguide/format_parse/messages/#examples)
for
[ICU4J](https://unicode-org.github.io/icu-docs/apidoc/released/icu4j/com/ibm/icu/text/MessageFormat.html).
This adds new syntax to the current Flutter messageFormat parser which
should allow developers to add locale-specific date formatting.

## Usage example
```
  "datetimeTest": "Today is {today, date, ::yMd}",
  "@datetimeTest": {
    "placeholders": {
      "today": {
        "description": "The date placeholder",
        "type": "DateTime"
      }
    }
  }
```
compiles to
```
  String datetimeTest(DateTime today) {
    String _temp0 = intl.DateFormat.yMd(localeName).format(today);
    return 'Today is $_temp0';
  }
```

Fixes https://github.com/flutter/flutter/issues/127304.

See https://docs.flutter.dev/reference/supported-platforms

I don't expect this to break anything, but if it does we can revert and figure out what else needs to happen first.

Without this change, engine changes upstream will get flagged in default flutter created apps.

Fix Gradle warning in a freshly `flutter create`ed Android project

Bump lower Dart SDK constraints to 3.0 & add class modifiers

This reverts commit 0fb4406c.

This reverts commit e03029ef.

* dart fix --apply

* manual fixes

* fix after merge conflicts

* review

* remove implicit no-sound-null-safety

* add test

* bump sdk constraint in test file

* Roll Flutter Engine from 67254d6e4b03 to 8d83b98c55b3

* Roll Dart SDK from 35a9facce191 to e517487c5679 (Dart 3.0) (#38105)

* Bump SDK versions.

* Bump Dart SDK version constraints

* Update shrine package to 2.0.1 (null safe version)

* Fix more tests.

* Include patches from Jason for min android sdk version

* Fix analyzer warning

* init

* code generation

* improve syntax error, add tests

* add tests and fix bugs

* code generation fix

* fix all tests :)

* fix bug

* init

* fix all code gen issues

* FIXED ALL TESTS :D

* add license

* remove trailing spaces

* remove print

* tests fix

* specify type annotation

* fix test

* lint

* fix todos

* fix subclass issues

* final fix; flutter gallery runs

* escaping for later pr

* fix comment

* address PR comments

* more

* more descriptive errors

* last fixes

Fixes #79439.

* Fix issues running integration tests through DAP

These adapters were incorrectly trying to connect a DDS instance even when Flutter would create its own. This change disables DDS in the DAP layer and leaves it to Flutter (although it passes `--no-dds` on to Flutter if provided to the DAP process).

Also fixes an issue where we would unnecessarily connect the VM Service for tests even in 'noDebug' mode because of a change/fix that now includes a 'vmServiceUri' in the `test.startedProcess` event.

* Use single quotes for `dartSdkVersionBounds`

* Update update_packages_test.dart

* Update test_project.dart

* Update tests_project.dart

* Update compile_error_project.dart

* Update hot_reload_with_asset.dart

* Update break_on_framework_exceptions_test.dart

* Update basic_project.dart

On Windows modified timestamps are round down to a second, which can lead to missed file updates.

Fixes https://github.com/flutter/flutter/issues/96677