This reverts commit 5fd259be.

This reverts commit d056500b.

This reverts commit 31de052e.

This reverts commit e2490f29.

Migrate flutter_localizations to null safety.

* Remove nullOk from cupertino color resolution

* Add CupertinoDynamicColor.maybeResolveFrom

* Remove CupertinoDynamicColor.maybeResolveFrom again

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.

* migrate some cupertino files to nullsafety

* address review comments

https://github.com/flutter/flutter/issues/31931

* add language version 2.8 in packages/flutter

* enable non-nullable analyzer flag

* add key to constructors of public widgets

* fix a test

* fix a test

* 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.