This CP lands PR https://github.com/flutter/flutter/pull/129856 into `stable`.
The PR above was part of a engine+framework change that got split in half during the stable cut, so now users are seeing some warnings that they can't act on.
(Those warnings were only intended for people who were using our methods manually, rather than using normal flutter tooling).
## Issues
Fixes https://github.com/flutter/flutter/issues/133069
* 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
* Allow sending messages from the platform to the framework
* Add ability to send messages from the plugin to the platform.
Also adds [PluginEventChannel] which is the plugin counterpart to
EventChannel.
Fixes https://github.com/flutter/flutter/issues/39981
* fix analyzer errors
* Enhance doc comments
* Remove dead code in test
