28846 Fixes FlutterSemanticsScrollView to not implement accessibility conta… (platform-ios, cla: yes, needs tests)

28850 fuchsia: Change flatland present’s release fence logic (cla: yes, platform-fuchsia, needs tests)

28863 [fuchsia] Remove unused deps on fidl optional.h. (cla: yes, waiting for tree to go green, platform-fuchsia, needs tests)

28903 Use the systrace recorder if systracing is enabled at startup, and enable systracing in release mode on Android (platform-android, cla: yes, waiting for tree to go green, needs tests)

28921 Deprecate SplashScreenProvider (platform-android, cla: yes, needs tests)

28923 [fuchsia] Dart Runner for CF v2 components. (cla: yes, platform-fuchsia, needs tests)