79807 Migrate some workflows and doctor validators to null safety (a: null-safety, cla: yes, team, tool)

79813 Migrate intellij_validator to null safety (a: null-safety, cla: yes, team, tool)

79816 Fix an NNBD error in the Gallery text form field demo (cla: yes, f: material design, team, waiting for tree to go green)

79900 Move cache from globals to globals_null_migrated (a: null-safety, cla: yes, team, tool)

79903 Revert “Reland [devicelab] Migrate Gallery to BuildTestTask” (a: accessibility, cla: yes, team)

79907 Migrate flutter_tool test/src/common to null safety (a: null-safety, cla: yes, team, tool)