26649 [web] migrate more felt code to null safety (cla: yes, platform-web)

26650 Roll Skia from 031d76b67447 to 163cc9124259 (1 revision) (cla: yes, waiting for tree to go green)

26651 Roll Skia from 163cc9124259 to 6b2121d0ec57 (4 revisions) (cla: yes, waiting for tree to go green)

26652 Roll Dart SDK from 37338b2f4bbb to 4dc4671c3a87 (1 revision) (cla: yes, waiting for tree to go green)

26653 Roll Fuchsia Mac SDK from qDntzygjT… to Q22GCF6Le… (cla: yes, waiting for tree to go green)