18802 Mark symbols that should be public (cla: yes)

18806 Roll Dart SDK from 54adfeb93f0b to e5b2cb0b02ae (53 revisions) (cla: yes, waiting for tree to go green)

18809 Support AOT mode in GTK shell (cla: yes)

18810 Don’t call engine when not initialized. (cla: yes)

18811 [web] Fix conic to quad conversion assertion. (cla: yes)

18814 Allow texture sampling quality control (cla: yes, platform-android, platform-ios)

18815 fix AttachCurrentThread override thread name issue (cla: yes, waiting for tree to go green)

18816 Fixes UI freezes when multiple Flutter VC shared one engine (cla: yes, platform-ios)