81528 Enable lock-thread based on github actions. (team, cla: yes, waiting for tree to go green)

81578 Enable library_private_types_in_public_api lint (a: tests, team, tool, framework, f: material design, a: accessibility, cla: yes, f: cupertino, d: examples, waiting for tree to go green)

81585 test macos binaries are codesigned before publishing (team, cla: yes, waiting for tree to go green)

81624 sort directives (team, tool, cla: yes, waiting for tree to go green)

81630 migrate web_complie_tests to null safety (team, cla: yes, waiting for tree to go green)

81633 Remove jcenter from build.gradle (team, cla: yes, waiting for tree to go green)