68034 [NNBD] Migrate some Widgets tests (a: tests, cla: yes, framework, team, waiting for tree to go green)

68038 Mark unusuallyLongTimeout as internal (a: tests, cla: yes, framework, waiting for tree to go green)

68065 Improve performance of collectAllElements (a: tests, cla: yes, framework, perf: speed, severe: performance, t: flutter driver, team, waiting for tree to go green)

68135 [flutter_releases] Flutter 1.22.2 framework cherrypicks (a: tests, cla: yes, engine, f: cupertino, f: material design, framework, team, tool)

68157 [NNBD] Migrate some Widgets tests (a: null-safety, a: tests, cla: yes, framework, team, waiting for tree to go green)