67827 [flutter_tools] Make ApplicationPackageFactory inject dependencies for Android Builds (cla: yes, tool)

67837 [flutter_tools] use fixed entry for dill uploads (cla: yes, tool)

67839 [flutter_tools] verify checksum of downloaded artifacts (cla: yes, tool)

67849 Migrate even more widget framework tests to null safety. (a: accessibility, cla: yes, framework)

67860 [Improvement] Add prefix Alignment. for toString of Alignment (cla: yes, framework)

67882 [flutter_tools] HACKTOBERFEST (cla: yes, tool)

67883 [flutter_tools] validate that SkSL bundle path exists (cla: yes, tool)

67884 [flutter_tools] document flutter root initialization (cla: yes, tool)