63799 bug fix for flutter_gallery__transition_perf(_with_semantics) (a: accessibility, cla: yes, team)

63801 Mark nonflaky tests as such (cla: yes, team, waiting for tree to go green)

63804 drop xcpretty for tests (cla: yes, team)

63815 [flutter_tools] correctly forward error only stdout in non-verbose modes (cla: yes, team, tool, waiting for tree to go green)

63983 In macrobenchmarks e2e tests: ensureVisible => scrollUntilVisible (cla: yes, team, waiting for tree to go green)

63995 Make cirrus tests presubmit only and add new luci tests. (cla: yes, team, waiting for tree to go green)