65481 Remove mac prod builder. (cla: yes, team)

65482 Revert “Re-land ScaffoldMessenger” (cla: yes, f: material design, framework)

65488 Revert “Nnbd widgets” (a: accessibility, cla: yes, f: cupertino, framework)

65490 [flutter_tools] remove globals from tracing and add unit tests (cla: yes, tool, waiting for tree to go green)

65493 Always use POSIX paths for generated CMake files (cla: yes, tool)

65511 Update Windows app template (cla: yes, tool, waiting for tree to go green)