20417 Add virtual destructors to ByteStream* (cla: yes)

20420 Add missing reply in C++ MethodChannel unit test (cla: yes)

20421 Make CkVertices a ManagedSkiaObject (cla: yes)

20422 Fix broken shell_unittests on Fuchsia (affects: tests, cla: yes, platform-fuchsia)

20425 Custom Gradle home and add .vpython file (cla: yes, waiting for tree to go green)

20426 Delete CSS paint code (cla: yes)

20427 Add –unoptimized and –asan to Fuchsia builds (cla: yes, platform-fuchsia)

20446 Engine 1.20.2 cherrypicks (cla: yes, platform-ios)