21790 Call PlatformView.dispose when removing hybrid composition platform views (cla: yes, platform-android)

21792 Revert “Migration to PlatformDispatcher and multi-window #20496” (cla: yes, platform-android, platform-ios, waiting for tree to go green)

21794 Roll Skia from ab6e62c131e9 to f58db3c94da3 (6 revisions) (cla: yes, waiting for tree to go green)

21795 Roll Fuchsia Mac SDK from FFpTJfmj1… to 8Cb2zG9e3… (cla: yes, waiting for tree to go green)

21797 Roll Fuchsia Linux SDK from h-DeV4tgE… to gdo4mZ5oI… (cla: yes, waiting for tree to go green)