83136 Roll Flutter Gallery with Gradle pinned dependencies (team, cla: yes, waiting for tree to go green)

83137 Move globals.artifacts to globals_null_migrated, update imports (team, tool, cla: yes, waiting for tree to go green, a: null-safety)

83146 Add iOS key map generation, make macOS var naming consistent with repo (team, framework, cla: yes)

83147 Migrate build_system, exceptions, and source to null safety (team, tool, cla: yes, waiting for tree to go green, a: null-safety)

83153 Migrate compile to null safety (team, tool, cla: yes, waiting for tree to go green, a: null-safety)

83160 Refactor android_view example (team, cla: yes, waiting for tree to go green)