9452 Convert RRect.scaleRadii to public method (affects: framework, cla: yes)

9456 Made sure that the run_tests script returns the right error code. (cla: yes)

9458 Test cleanup geometry_test.dart  (affects: tests, cla: yes)

9459 Remove unused/unimplemented shell constructor (cla: yes)

9460 Fixed logLevel filter bug so that filter now works as expected. (cla: yes)

9461 Adds API for retaining intermediate engine layers (cla: yes)

9462 Reland Update harfbuzz to 2.5.2 (cla: yes)

9463 Removed unused imports in new embedding. (cla: yes)

9464 Added shebangs to ios unit test scripts. (cla: yes)