71439 [fluttter_tools] reland enable experimental invalidation strategy on by default in master channel (cla: yes, tool)

71446 Relands: Migrate template to Gradle 6.7 and AGP 4.1.0 (a: accessibility, cla: yes, d: examples, team, tool)

71450 Upgrade deps (cla: yes, team, waiting for tree to go green)

71451 Validate empty observatory URI for screenshot (cla: yes, tool, waiting for tree to go green)

71459 Revert “Fix excessive rebuilds of DSS” (cla: yes, framework)

71487 [flutter_tools] report basic analytics for null-safety (cla: yes, tool)