21526 iOS: only add explicit transactions when there are platform views (only on main threads) (cla: yes, platform-ios, waiting for tree to go green)

21578 Use absolute path in ios_test_flutter target (cla: yes, platform-ios, waiting for tree to go green)

21632 Add flag to not publish the observatory port over mDNS (cla: yes, platform-ios)

21669 [flutter_releases] Flutter 1.22.1 Engine Cherrypicks (cla: yes, platform-android, platform-ios)

21679 [flutter_releases] fix infra failure for web framework tests (cla: yes, platform-android, platform-ios)

21694 Skip flaky test (cla: yes, platform-ios)