25612 Add Metal to the FlutterCompositor struct in the Embedder API (cla: yes, embedder)

25613 Roll Skia from 333de882b62c to 665920e9b9fb (7 revisions) (cla: yes, waiting for tree to go green)

25614 Fix drawVertices when using indices for web_html (cla: yes, platform-web)

25615 Remove –dartdocs in preparation for removal from tool (cla: yes)

25616 migrate tests to nullsafe (cla: yes, platform-web)

25617 kick build (cla: yes)

25618 Roll Skia from 665920e9b9fb to 096226809997 (8 revisions) (cla: yes, waiting for tree to go green)