67012 Replace MockArtifacts with Artifacts.test() (cla: yes, team, tool)

67019 Replace MockProcessManager with FakeProcessManager (cla: yes, team, tool, waiting for tree to go green)

67025 Fix docset generation. (cla: yes, team)

67057 update stack_trace dep (and others) (cla: yes, team, tool, waiting for tree to go green)

67147 5x startup test repitition to reduce noise (cla: yes, customer: money (g3), perf: speed, severe: performance, team, waiting for tree to go green)

67155 [null-safety] migrate app dependencies of flutter driver (a: accessibility, a: null-safety, a: tests, cla: yes, framework, team)