This was missing the actual opacity rendering, oops

Updates most of the unit tests in the packages/flutter/test/material folder so that they'll pass if ThemeData.useMaterial3 defaults to true.

All of the tests have wired useMaterial3 to false and will need to be updated with a M3 version.

related to #127064

Adds a special opacity widget that does not act like a repaint boundary.

Better solution for https://github.com/flutter/flutter/pull/128138

Fixes https://github.com/flutter/flutter/issues/127836

The flexible scroll bar needs to rebuild even if the child/opacity hasn't changed. Force this with a value key.

To opt-in, run the tests with: `SKPARAGRAPH_REMOVE_ROUNDING_HACK=1 flutter test --dart-define=SKPARAGRAPH_REMOVE_ROUNDING_HACK=1 `

Migration plans:
1. Turn the flags on in CI, migrate customer tests if needed
1. Migrate internal customers
2. Remove the flag from skparagraph. Remove the framework flag with a manual engine roll.

Also fixes https://github.com/flutter/flutter/issues/52038

* Fix position of CupertinoContextMenu within Transform.scale (#97896)

* Fix after rebase

This reverts commit 6ddb99e9.

This reverts commit c82ddd39.

* Reland "Android Q transition by default (#82670)"

This reverts commit 4053b4b1.

* Fix `overall_experience_test.dart` for flutter_tools

This reverts commit a1ae4fea.

Revert "Revert "Fix FlexibleSpaceBar Opacity when AppBar.toolbarHeight > ktoolbarHeight (#80453)" (#80545)" (#80589)

Adds MediaQuery.maybeOf to replace calling MediaQuery.of(context, nullOk: true), and removes the nullOk parameter. Also changes MediaQuery.of to return a non-nullable value, and removes many instances of the ! operator, reducing the possible places where a null dereference could occur.

Just converting some test files to NNBD

* add language version 2.8 in packages/flutter

* enable non-nullable analyzer flag

Add width constraints for FlexibleSpaceBar.title in its expanded state, so that overflow of long titles can be handled (#51335)

This PR adds the linux and windows target platform enum values, along with automatically setting the defaultTargetPlatform to the appropriate value on those platforms.

Fixes #31366

[a11y] Make sure RenderFractionalTranslation updates its semantics after the translation field is set (#48985)

This contains the test changes for adding TargetPlatform.macOS, which was done in #43457.

The main goal of this PR is to enable tests in the material library that are currently running only on iOS to also run on macOS, but only for the tests where that makes sense. For instance, we don't run any of the haptic feedback tests on macOS.

* Update project.pbxproj files to say Flutter rather than Chromium

Also, the templates now have an empty organization so that we don't cause people to give their apps a Flutter copyright.

* Update the copyright notice checker to require a standard notice on all files

* Update copyrights on Dart files. (This was a mechanical commit.)

* Fix weird license headers on Dart files that deviate from our conventions; relicense Shrine.

Some were already marked "The Flutter Authors", not clear why. Their
dates have been normalized. Some were missing the blank line after the
license. Some were randomly different in trivial ways for no apparent
reason (e.g. missing the trailing period).

* Clean up the copyrights in non-Dart files. (Manual edits.)

Also, make sure templates don't have copyrights.

* Fix some more ORGANIZATIONNAMEs

* add missing trailing commas

* add more missing trailing commas

* add more and more missing trailing commas