84065 Migrate gallery test to null safety (team, a: accessibility, cla: yes, waiting for tree to go green, a: null-safety, tech-debt)

84136 Migrate android_semantics_testing to null safety (team, a: accessibility, cla: yes, waiting for tree to go green, a: null-safety, tech-debt)

84154 Revert “Migrate android_semantics_testing to null safety (#84136)” (team, a: accessibility, cla: yes)

84156 Re-land “Migrate android_semantics_testing to null safety (#84136)” (team, a: accessibility, cla: yes, waiting for tree to go green, a: null-safety, tech-debt)