This implements dual compile via the newly available flutter.js bootstrapping APIs for intelligent build fallback.
* Users can now use the `FlutterLoader.load` API from flutter.js
* Flutter tool injects build info into the `index.html` of the user so that the bootstrapper knows which build variants are available to bootstrap
* The semantics of the `--wasm` flag for `flutter build web` have changed:
  - Instead of producing a separate `build/web_wasm` directory, the output goes to the `build/web` directory like a normal web build
  - Produces a dual build that contains two build variants: dart2wasm+skwasm and dart2js+CanvasKit. The dart2wasm+skwasm will only work on Chrome in a cross-origin isolated context, all other environments will fall back to dart2js+CanvasKit.
  - `--wasm` and `--web-renderer` are now mutually exclusive. Since there are multiple build variants with `--wasm`, the web renderer cannot be expressed via a single command-line flag. For now, we are hard coding what build variants are produced with the `--wasm` flag, but I plan on making this more customizable in the future.
* Build targets now can optionally provide a "build key" which can uniquely identify any specific parameterization of that build target. This way, the build target can invalidate itself by changing its build key. This works a bit better than just stuffing everything into the environment defines because (a) it doesn't invalidate the entire build, just the targets which are affected and (b) settings for multiple build variants don't translate well to the flat map of environment defines.

Fixes https://github.com/flutter/flutter/issues/140169

Revert "Make tests more resilient to Skia gold failures and refactor flutter_goldens for extensive technical debt removal (#140101)" (#141814)

Reverts https://github.com/flutter/flutter/pull/140101

That PR somehow made non-matching gold tests not fail at HEAD.

Fixes https://github.com/flutter/flutter/issues/141880
- Blocked by https://github.com/flutter/flutter/issues/140169
  - https://github.com/flutter/flutter/pull/141427

Fixes https://github.com/flutter/flutter/issues/141032

We pinned to web_socket_channel v2.4.1 because v2.4.2 was retracted, however v2.4.3 is now available.

Work around https://github.com/flutter/flutter/issues/141032

Otherwise a re-land of https://github.com/flutter/flutter/pull/140979

Fixes https://github.com/flutter/flutter/issues/137163 & https://github.com/flutter/flutter/issues/139181

Reverts flutter/flutter#140979
Initiated by: loic-sharma
This change reverts the following previous change:
Original Description:
Fixes https://github.com/flutter/flutter/issues/137163
Fixes https://github.com/flutter/flutter/issues/139181

Fixes https://github.com/flutter/flutter/issues/137163
Fixes https://github.com/flutter/flutter/issues/139181

This PR was generated by `flutter update-packages --force-upgrade`.

Contributes to: https://github.com/flutter/flutter/issues/135856

1. Move leak_tracker and leak_tracker_testing out of direct dependencies.
2. Move leak_tracker_flutter_testing from dev to prod dependencies for flutter_test

It is prerequisite for https://github.com/flutter/flutter/issues/135856

Pinning the package:web dependency constrains downstream packages from
using newer versions and making sure they support the version pinned in
Flutter. Since the usage of package:web in Flutter is light, we should
instead have a small shim like the engine and keep package:web as a dev
dependency only.

Contributes to https://github.com/flutter/flutter/issues/135856

test-exempt: rolling dependencies

This version is needed so that dart:js_interop can move to extension
types. Also adds some code to handle some breaking changes:

- Body -> Response. Body was an IDL interface mixin type we exposed in
dart:html. Going forward, users should either use Request or Response.
- Casts to JSAny. These are temporary until we move package:web types to
extension types. Currently, package:web types can't implement JSObject
as JSObject will move to be an extension type itself.
Co-authored-by: Kevin Moore <kevmoo@users.noreply.github.com>

https://github.com/flutter/engine/pull/46829 changed event handling
sequence on web so that KeyboardBinding/RawKeyboard handles the text
event first before it reaches IME. That means when dispatching
synthetised events to IME every keydown event must have a corresponding
keyup, otherwise consistency assertions in `KeyboardBindings` are
triggered.

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel
on [Discord].

<!-- Links -->
[Contributor Guide]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#overview
[Tree Hygiene]: https://github.com/flutter/flutter/wiki/Tree-hygiene
[test-exempt]:
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https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo
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Analyzer's dependency on autosnapshotting causes issues.

Because every version of integration_test from sdk depends on leak_tracker from hosted and autosnapshotting depends on leak_tracker from path, integration_test from sdk is forbidden.
So, because autosnapshotting depends on integration_test from sdk, version solving failed.

Contributes to: https://github.com/flutter/flutter/issues/135856

This PR also adds transitive dependency on  web_socket_channel, crypto, typed_data. `web_socket_channel` is needed to request retaining path for not GCed objects from VM Service. Two others are needed to serve web_socket_channel.

The dependency on leak_tracker is pinned:
https://github.com/flutter/flutter/blob/aea562114c4d8c220c9079e82d89a7da4164409f/packages/flutter_tools/lib/src/commands/update_packages.dart#L40

This PR was generated by `flutter update-packages --force-upgrade`.

Generated by running `flutter update-packages --force-upgrade`

Updates vm_service to [12.0.0](https://pub.dev/packages/vm_service/versions/12.0.0) and dwds to [22.0.0](https://pub.dev/packages/dwds/versions/22.0.0)

The changes to `packages/flutter_tools/lib/src/isolated/devfs_web.dart` are for the new interface of DWDS introduced in https://github.com/dart-lang/webdev/pull/2243

FYI @bkonyi

* Allow latest pkg:material_color_utilities
* Bump other dependencies to their latest - including pkg:web

Fixes: https://github.com/flutter/flutter/issues/135716
leak_tracker is left pinned because future updates are going to be breaking.

This PR is the result of running:

```console
$ flutter upgrade-packages --force-upgrade
```

### Issues

* Fixes https://github.com/flutter/flutter/issues/135075
* Supersedes #135081

More up to date version of https://github.com/flutter/flutter/pull/133786.

Fixes https://github.com/flutter/flutter/issues/111304

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.

Generated by running `flutter update-packages --force-upgrade`

Reverts flutter/flutter#131998

Reverting for https://github.com/flutter/flutter/issues/132222

Dart SDK 3.2.x requires a new version of the dart_internal package.