27893 Adds semantics tooltip support (platform-android, cla: yes, waiting for tree to go green, platform-fuchsia, embedder)

27896 Roll Skia from f3868628f987 to b806da450199 (6 revisions) (cla: yes, waiting for tree to go green)

27897 fuchsia: Fix thread names + add test (cla: yes, waiting for tree to go green, platform-fuchsia)

27898 Roll buildroot (cla: yes, waiting for tree to go green)

27899 Embed OCMock and iOS tests into IosUnitTests app (platform-ios, cla: yes, waiting for tree to go green)

27900 Remove references to deprecated SkClipOps (cla: yes, waiting for tree to go green, needs tests)