74078 Roll Engine from a243f4df0711 to 1424dfbe4d57 (6 revisions) (cla: yes, waiting for tree to go green, will affect goldens)

74079 [flutter_tools] verify successful dart migrate (cla: yes, tool, waiting for tree to go green)

74080 Add verbose build flag to ios_app_with_extensions_test (a: tests, cla: yes, team)

74088 Revert “Improve the ScrollBar behavior when nested” (cla: yes, f: cupertino, f: material design, framework)

74089 Update the alt text to match recommendations in HTML spec (cla: yes, framework, waiting for tree to go green)

74090 Tests that module/plugin/package templates can be migrated to null-safety (cla: yes, tool, waiting for tree to go green)