68207 Revert “Improve performance of collectAllElements” (a: tests, cla: yes, framework, team)

68214 reland List queue search optimization (a: tests, cla: yes, framework, team)

68301 use_is_even_rather_than_modulo (a: accessibility, a: tests, cla: yes, f: material design, framework, team)

68302 enable unnecessary_string_escapes and use_raw_strings (a: internationalization, a: tests, cla: yes, f: cupertino, f: material design, framework, team, tool, waiting for tree to go green)

68505 Updated one reference to FlatButton in real_tests/extension_test.dart (a: tests, cla: yes, framework)