Flutter's `moreOrLessEquals` has a few advantages over `closeTo` from
the `matcher` package:

   * It emits the epsilon value in the test result on failure.
   * It uses a named parameter for epsilon, which improves readability
     at the call site.
   * It has a reasonable default for epsilon in cases where something
     more specific isn't required.

Using it also has the nice property that it aids in its own discovery
when when people go looking for such functionality in new tests.

This change also includes a couple unrelated whitespace formatting cleanups.

This reverts commit b3c237ce.

* add language version 2.8 in packages/flutter

* enable non-nullable analyzer flag

This reverts commit 8de07d55.

This reverts commit d9882263.

Unrevert of paste button hides when nothing to paste

This reverts commit d5634982.

Unreverts #54902 with fixes for a failing integration test.

This reverts commit 053c3881.

* replace simple Container(w & h) with SizedBox

* address review comments

* address review comments

Use strut box heights to calculate selection rectangles in order to ensure that they remain within visible bounds (#50354)

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

Add TargetPlatform.macOS tests to cupertino, foundation, rendering, and services libraries. (#45644)

This PR rewrites MouseTracker's lifecycle, so that mouse callbacks are all triggered in post frame, instead of the current one where some are triggered during the build phase. This PR also changes the onExit callback to MouseRegion, RenderMouseRegion, and MouseTrackerAnnotation, so that it is no longer triggered on dispose.

* 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

This reverts commit 8df0d655.

This disables the arrow key focus navigation for text fields. This was non-standard behavior for text fields, although it remains useful for other kinds of controls.

Fixes #42259

* add missing trailing commas

* add more missing trailing commas

* add more and more missing trailing commas