24263 Fix retain cycles in MacOS embedder (cla: yes)

24264 Unblock FlutterResizeSynchronizer on engine shutdown (cla: yes, waiting for tree to go green)

24265 Roll Skia from c0f981560985 to 827f8c010319 (5 revisions) (cla: yes, waiting for tree to go green)

24268 Roll Dart SDK from daf7b29738c5 to 85af45218196 (2 revisions) (cla: yes, waiting for tree to go green)

24269 Roll Dart SDK from 85af45218196 to b74a0c8d6786 (1 revision) (cla: yes, waiting for tree to go green)