79329 fix tree (cla: yes, team)

79332 Point gallery test data to FLUTTER_TEST_OUTPUTS_DIR (cla: yes, team, team: infra, waiting for tree to go green)

79342 Migrate code_signing to null safety (a: null-safety, cla: yes, team, tool)

79346 Migrate event_printer and test_config to null safety (a: null-safety, cla: yes, team, tool, waiting for tree to go green)

79394 Remove animation_with_microtasks_perf_ios__timeline_summary from prod… (cla: yes, team, waiting for tree to go green)

79396 Create dev/ci.yaml (cla: yes, team, waiting for tree to go green)