26693 Revert “Add support for native callbacks to the macOS embedder test harness” (cla: yes, platform-macos)

26694 Add support for native callbacks to the macOS embedder test harness (cla: yes, platform-macos)

27189 MacOS: Release backbuffer surface when idle (cla: yes, waiting for tree to go green, platform-macos, needs tests)

27191 MacOS (metal): Block raster thread instead of platform thread (cla: yes, waiting for tree to go green, platform-macos, needs tests)

27354 Ensure gclient sync is successful on an M1 Mac host. (cla: yes, waiting for tree to go green, platform-macos)

27465 Add a unit test for dart entrypoint args on macOS (cla: yes, platform-macos)