58622 Don’t elapse real time during IOSDevice.startApp tests (cla: yes, team, tool, waiting for tree to go green)

58630 Updated Slider test  (cla: yes, f: material design, framework, waiting for tree to go green)

58635 Remove DiagnosticableMixin in favor of Diagnosticable (cla: yes, framework, team, waiting for tree to go green)

58644 Add FakeAsync to delay tests (cla: yes, team, tool)

58645 Move create project build tests to permeable command shard (cla: yes, team, tool)

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