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.

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.

Updated references to the old button classes to the new ones in comments and documentation for tests in the material and cupertino libraries. (#62164)

* Add semantics sort key for modal scope and modal barrier

* fix test

* fix test

* fix test

* fix space

* fix more tests

* addressing comments

* add language version 2.8 in packages/flutter

* enable non-nullable analyzer flag

* 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

No code changes, just comments: I spell-checked all the comments in the repo.

Fixes #42049.

Make font semibold when isDefaultAction is true in CupertinoDialogAction

* add trailing commas on list/map/parameters

* add trailing commas on Invocation with nb of arg>1

* add commas for widget containing widgets

* add trailing commas if instantiation contains trailing comma

* revert bad change

* Refactor of cupertino/material/widgets app

* update docs 

* Update tests for const

This reverts commit 61cf946b.

* Make CupertinoApp and MaterialApp both use WidgetsApp for Navigator

* Make CupertinoApp and MaterialApp const constructors

* Make WidgetsApp routes aware

* Update tests

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests

Fixes #21250

Rewrote CupertinoAlertDialog to look nearly identical to an alert dialog in iOS. This includes considerations for blur, translucent white background color, button sizing, gap dividers between buttons, and text scaling layout behavior. (#18381)

It was causing problems rolling Flutter into Fuchsia