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

68107 [devicelab] delete disabled or not useful benchmarks (cla: yes, team)

68109 [devicelab] mark ios catalina as flaky (cla: yes, team)

68110 [devicelab] turn down android X migration gradle tests (cla: yes, team)

68132 Update package:stack_trace dependency to 1.10.0-nullsafety.4 (cla: yes, team, tool)

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