This reverts commit ab51a026 and fixes the test that broke the first time it landed.

This reverts commit 885b2f56 to green up the build.

Submitting on red to fix the build.

In the process of fixing #90044, I realized that it's also possible for hovered tooltips to show more than one at a time if the widgets are nested, so this PR is a fix that prevents more than one tooltip from showing at a time with hovered tooltips.

This reverts commit 35ad43f2.

This reverts commit c26ed03c.

* Migrate to ChannelBuffers.push

* Move TestDefaultBinaryMessenger to its own file

* Apply deprecations and fix usages

* 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

* replace simple Container(w & h) with SizedBox

* address review comments

* address review comments

* 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

* Fix Tooltip Directionality

* Add regression test comment for tooltip directionality fix

* add missing trailing commas

* add more missing trailing commas

* add more and more missing trailing commas