18553 null-annotate semantics.dart (cla: yes)

18555 null-annotate lib/ui/hooks.dart (cla: yes)

18556 Roll Dart SDK from d551980ac9fc to ecce58c1e354 (2 revisions) (cla: yes, waiting for tree to go green)

18557 Roll Skia from 22636205ce92 to b37105ea6cca (2 revisions) (cla: yes, waiting for tree to go green)

18558 Roll Fuchsia Mac SDK from RNByJ… to _zNmv… (cla: yes, waiting for tree to go green)