70026 [flutter_tools] Let CMake handle escaping (cla: yes, tool, waiting for tree to go green)

70056 [flutter_tools] restore pub caching functionality (cla: yes, tool)

70058 [flutter_tools] remove branch migration and standardize constructor style for version interface (cla: yes, tool, work in progress; do not review)

70065 [flutter_tools] improve hash performance (cla: yes, tool)

70078 Roll engine and fix pubspecs that do not have a Dart SDK constraint (cla: yes, engine, team, tool)

70116 Migrate Flutter Gallery test to null safety (cla: yes, f: cupertino, f: material design, team, tool)

70120 default to unsound nullability for web (cla: yes, tool, waiting for tree to go green)