66375 Provide defaulting for textScaleFactor when passing to dart:ui (a: typography, cla: yes, framework, waiting for tree to go green)

66379 Remove last FakeImage implementation (cla: yes, framework)

66387 enable lint unnecessary_nullable_for_final_variable_declarations (cla: yes, framework)

66409 Change emoji in About dialog to be a divider (cla: yes, f: material design, framework, waiting for tree to go green)

66418 fix nullability issues (cla: yes, f: cupertino, framework)

66424 migrate some cupertino files to nullsafety (cla: yes, f: cupertino, framework, waiting for tree to go green)