58646 Flutter 1.17.3 cherrypicks (a: accessibility, cla: yes, d: examples, engine, f: cupertino, f: material design, framework, team, tool)

59186 Opt out nnbd in packages/flutter (a: accessibility, cla: yes, f: cupertino, f: material design, framework)

59219 Typo fixing sweep through packages/flutter. (a: accessibility, cla: yes, f: cupertino, f: material design, framework, waiting for tree to go green)

59617 Reland modernize selection menu appearance (a: accessibility, a: internationalization, cla: yes, f: cupertino, f: material design, framework, team, waiting for tree to go green)

60141 Tweaking Material Chip a11y semantics to match buttons (a: accessibility, cla: yes, customer: money (g3), f: material design, framework)