* Upgrade everything except matcher.
* Roll matcher (and test)
* Adjust tests that depend on flutter:test directly to depend on a shim
* Require use of package:test shim and remove other references to package:test

* Adding a setup function for hot restart that can be overwritten to perform any necessary initialization before a restart is started.

* Adding a test for setupHotRestart

* Removing local pubspec change

* Fixing some type annotation errors

* Responding to comments

Fixes https://github.com/flutter/flutter/issues/14517
Or at least, fixes the crash part of that.

See https://github.com/flutter/flutter/issues/7248