67477 Migrate some material tests to nnbd (cla: yes, f: material design, framework)

67482 Migrate More Material Tests (cla: yes, f: material design, framework, waiting for tree to go green)

67525 unnecessary null comparison (a: tests, cla: yes, f: material design, framework, waiting for tree to go green)

67545 Reland removal of examples/catalog (a: accessibility, cla: yes, d: examples, f: material design, framework, team, waiting for tree to go green)

67552 [flutter_releases] Flutter 1.22.1 Framework Cherrypicks (cla: yes, engine, f: material design, framework, team, tool)

67556 Migrate Material framework tests to null safety (cla: yes, f: material design, framework)