77942 Refactor: use one subprojects property (a: accessibility, cla: yes, d: examples, team, tool, waiting for tree to go green)

78143 Update docs to reflect Null Safety (cla: yes, d: api docs, d: examples, documentation, framework)

78623 Reverts “Implement dartPluginClass support for plugins #74469” (cla: yes, d: examples, team, tool)

78984 [SliverAppBar] Improve dartpad sample in documentation (cla: yes, d: api docs, d: examples, documentation, f: material design, framework, waiting for tree to go green)

79650 add trailing comma when argList is splitted (cla: yes, d: examples, f: cupertino, f: material design, framework, team, waiting for tree to go green)