81235 Migrate to ChannelBuffers.push (a: tests, team, framework, f: material design, a: accessibility, cla: yes, f: cupertino, d: examples, waiting for tree to go green)

81406 Add trailing commas in examples and packages/flutter/ (team, framework, f: material design, cla: yes, f: cupertino, d: examples)

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)

81706 Integrate MaterialBanner with the ScaffoldMessenger API (severe: new feature, framework, a: animation, f: material design, a: fidelity, cla: yes, d: api docs, d: examples, a: quality, waiting for tree to go green, documentation)