70327 [flutter_releases] Flutter 1.22.4 framework cherrypicks (a: tests, cla: yes, d: examples, engine, f: cupertino, f: material design, framework, team, tool)

70379 Added Tabar Code samples (adopt a widget, cla: yes, d: api docs, d: examples, documentation, f: material design, framework, waiting for tree to go green)

70382 Update FlexibleSpaceBar dartpad sample (adopt a widget, cla: yes, d: api docs, d: examples, documentation, f: material design, framework, waiting for tree to go green)

70808 Migrate template to Gradle 6.7 and AGP 4.1.0 (a: accessibility, cla: yes, d: examples, team, tool)