Use tester (disclaimer, written by me) to unit test the flutter tools general shard. Since these tests are designed to be hermetic, the single compilation/single isolate model offers a tremendous speedup over the default pub run test workflow. On previous linux shard, test execution alone took 10:30, while now it takes only 1:30.

Update all versions, specifically file which fixes some bugs that caused tests to fail if run in different orders:

- systemTemp directories created by MemoryFileSystem will allot names based on the file system instance instead of globally.
- MemoryFile.readAsLines()/readAsLinesSync() no longer treat a final newline in the file as the start of a new, empty line.
- RecordingFile.readAsLine()/readAsLinesSync() now always record a final newline.

Fixes #59718

Update all versions, specifically dwds which has a hot restart fix

Re-land "Deprecate WhitelistingTextInputFormatter and BlacklistingTextInputFormatter (#59120)" (#59876)

This relands #59120, which was reverted in #59870.

Revert "Deprecate WhitelistingTextInputFormatter and BlacklistingTextInputFormatter (#59120)" (#59870)

This reverts commit 8665e138.

[flutter_tools] ensure generated entrypoint matches test and web entrypoint language version (#59291)

Ensure that the language version of the test/web generated entrypoint matches the language version of the test file to run, or the overall package language version if no annotation is provided.

* Word substitutions

* ++

The flutter infra recipes got moved to a new location and we need to
update docs with links to the new locations.

Bug:
  https://github.com/flutter/flutter/issues/45630

Also combines experiments into extraGenSnapshot/ExtraFrontEndOptions. Allows providing --no-sound-null-safety to allow out of order migration and running.

* Run `flutter update-packages --force-upgrade`.
* Update test to 1.14.5.

Fixes #58003

The .dart_tool directory can contain build assets, as well as the package_config.json file - the replacement for .packages. Remove it for the same reason we remove .packages

An upcoming Dart SDK change
(https://github.com/dart-lang/sdk/commit/fa2fd41166db35afa4777e63f900e83d25709c5c)
changes the precise text of the exception generated by `utf8.decode`
if a non-UTF8 file is found.  This is causing a breakage in the Dart
team's `flutter-analyze` bot (and will presumably cause a breakage in
the corresponding Flutter bot as soon as this change is rolled into
Flutter).  To avoid this breakage, the bot shouldn't rely on the exact
exception text; it is sufficient to simply catch a FormatException.

Ensure iOS and android builds can be correctly cached. Use the performance-measurement-file to verify that all targets were skipped on the second invocation. This is only run on the flutter_gallery build.

Support --enable-experiment in flutter test (for flutter_tester). Required minor change for null safety.

This reverts commit 98651c02.