79969 Remove RunLoop from Windows template (tool, cla: yes)

79975 Use testUsingContext in downgrade_upgrade_integration_test (a: tests, team, tool, cla: yes, waiting for tree to go green)

79977 Tell user how to enable available but disabled features (tool, cla: yes)

79983 [flutter_tools] handle out of date xcode config in assemble (tool, cla: yes, waiting for tree to go green)

79985 Convert some general.shard base tests to null safety (team, tool, cla: yes, waiting for tree to go green, a: null-safety)

79989 Remove flutterNext (tool, cla: yes, platform-web, waiting for tree to go green, a: desktop)

79991 [flutter_tools] add timeline ANR integration test (tool, cla: yes, waiting for tree to go green)