79608 Remove “unnecessary” imports in test/widgets (tool, framework, cla: yes, waiting for tree to go green)

79669 Reland the Dart plugin registry (team, tool, cla: yes, d: examples, waiting for tree to go green)

79898 migrate empty exceptions to tool exit with error message (tool, cla: yes, waiting for tree to go green)

79905 Check if reg can run before calling it on Windows (tool, cla: yes)

79908 Start migrating flutter_tools test src to null safety (team, tool, cla: yes, waiting for tree to go green, a: null-safety)

79911 Migrate tool version to null safety (team, tool, cla: yes, a: null-safety)

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