[flutter_tools] separate concept of null safe language version from current language version (#79052)

This reverts commit 8b6baae4.

Our current top crasher is an unclear error when ProcessManager fails to resolve an executable path. To fix this, we'd like to being adjusting the process resolution logic and adding more instrumentation to track failures. In order to begin the process, the ProcessManager has been folded back into the flutter tool

* opt out the flutter tool

* oops EOF

* fix import

* Update tool_backend.dart

* Update daemon_client.dart

* fix more

Instead of using package:package_config to write the .dart_tool/package_config the original json is modified and rewritten.

The .dart_tool/package_config.json file is read twice to simplify control flow.

This also avoids the issue of package:package_config writing directly to local filesystem.

* NNBD gen-l10n generated code

Disabled caching of pub invocations on flutter drive.

This reverts commit ff953e4f.

Fixes #69416
Fixes #70121

Necessary to work around #70013 (this looks like it will be fixed, but should protect us in the future)

Restores some notion of skipping pub, with differences from the prior implementation:

Off by default, and only used by the flutter command automatic pub get
A single check parameter. Uses the framework version cached per-project instead of a timestamp of the tool, to avoid cases where downloading a prebuilt framework would cause this check to no longer work.

This reverts commit 6e5845f0.

There have been some more additional reports of a missing 'package:characters' import after upgrading flutter. This has me concerned that our pub caching logic is incorrect. Instead of the tool attempting to guess when pub should be run, always delegate to pub.

Also takes an opportunity to fix the kernel snapshot depending on the .packages or package_config. Due to the generated: date field this causes extra rebuilds. Instead when pub get is run, write out an additional file with just the package contents and version.

Fixes #66777
Fixes #65723

Remove "This is taking a long time" progress timeout and TimeoutConfiguration.

This reverts commit 76cbc462.

There have been some more additional reports of a missing 'package:characters' import after upgrading flutter, as well as problems with detecting the correct language version. This has me concerned that our pub caching logic is incorrect. Instead of the tool attempting to guess when pub should be run, always delegate to pub.

Split from #66776

Even if pub does not change the packge_config contents, it will still update a timestamp in one of the fields. This causes unnecessary rebuilds. To fix this, generate an additional file when running pub get that only contains the relevant fields and then update the KernelSnapshot rule to depend on it only.

No matter what level(error, warning, info) issues flutter analyze always return fatal exit code(1). CI/CD environment receive 1(!0). This may leads to e.g. Jenkins Build step 'Execute shell' marked build as failure.
I propose according to AnalysisSeverity level return fatal(1) or success(0) exit code.

[flutter_tools] use flutter tool handler for dwds resources and precache tool pub dependencies (#65814)

If the tool is downloaded from a precompiled snapshot, or if the backing source files in the pub cache are deleted, the dwds debugging functionality will break as the client.js file cannot be located. Instead use the PackageConfig to verify that package location, downloading if it is missing.

Override the dwds middleware to avoid Isolate.resolvePackageUri

Fixes #53644
Fixes #65475

* synthetic packages by default in gen_l10n tool

* Refactor default path for synthetic package

* Remove unused import

* Code cleanup

* Further improvements to help text

* Refactor synthetic package path

* Remove newlines

* Test cleanup

* clean up logic in inputs and outputs list function

* Update l10n.yaml usage

* only add option if value is non-null

* Update stocks app as proof of concept for synthetic package usage

* Address nits

* print pubspec contents

* add print statements

* Do not allow null value for useSyntheticPackage

* +

* +

* +

* +

* Cleanup

* Add test

* Fix text

* Dont parse pubspec directly

* Test using context

* WIP: generate synthetic packages on pub get -- needs tests

* Allow null value

* Update null handling

* Refactor to properly handle null case

* Fix yamlMap condition

* Fix yaml node for real

* WIP: struggling to write tests

* WIP - take absolute path as an option

* Add tests

* Use environment project directory for synthetic package generation pathway

* Fix typo

* Improve help text

* Update defaults

* Remove unauthorized path import

* Fix pathing issues at synthetic package generation

* Fix typo in test

* Use path.join so projectDir matches up based on OS

* Fix Windows pathing in test

* Remove unnecessary replaceApp code for projectDir.path

* Use globals.fs.currentDirectory.path in resident_runner_test.dart

* Fix merge conflict

* Add test to ensure that synthetic package is generated on pub get

* Fix resident_runner_test.dart tests

* Fix tests

* Use package:file instead of dart:io

* WIP - exploration

* Remove synthetic package use from stocks example

* Update integration test to not use synthetic packages

* Remove trailing whitespace

* flutter pub get runs synth package generation

* Remove more print statements

* Add license header

* WIP - minimally working pub.get

* Use own MockBuildSystem

* Modify test and implementation to be a little cleaner

* Fix flutter pub get invocation

* Use synthetic packages in stocks app

* Revert "Use synthetic packages in stocks app"

This reverts commit 45bf24903c3d4a2a5fd5481d7d6bc36c4a348703.

* Add environment and buildSystem params to flutter test

* Address code review feedback

* +

* Isolate codegen into its own API

* Fix imports

* Slight refactor

* Add one more test for no l10n.yaml file

* Remove unneeded mock class and import in pub_get_test.dart

* More code review feedback

* Remove unnecessary imports

* Remove `return await`s that I missed

* use arrow functions instead

Allow configuring the flutter_manifest to support a synthetic package, this is done through flutter: generate: true.

When running pub get, insert a flutter_gen entry into the packages if it does not already exist. This points to .dart_tool/flutter_gen, which can be updated to contain the generated intl sources (But doesn't currently)

Adds an integration test that verifies this code can be run and imported when enabled.

Part of #60914