76829 Remove dead ensureDirectoryExists (cla: yes, team, tool, waiting for tree to go green)

76830 Add ephemeral iOS directory to put future generated files (cla: yes, platform-ios, tool, waiting for tree to go green)

76833 Opt into CocoaPods parallel codesigning (cla: yes, platform-ios, t: xcode, tool, waiting for tree to go green)

76834 Stop trying to thin iOS App.framework (cla: yes, t: xcode, tool, waiting for tree to go green)

76884 [flutter_tools] remove all mock artifacts usage (cla: yes, tool)

76887 [flutter_tools] remove mocks from android SDK tests (cla: yes, tool, waiting for tree to go green)