69025 Reland: enable unnecessary_string_escapes and use_raw_strings (#68302) (a: internationalization, a: tests, cla: yes, f: cupertino, f: material design, framework, team, tool, waiting for tree to go green)

69041 Update null safe deps to prepare for the 2.12 sdk version (cla: yes, team, tool, waiting for tree to go green)

69043 [null-safety] add language version to freeform template (cla: yes, team)

69046 Print errors in all build modes (cla: yes, framework, team, waiting for tree to go green)

69048 Migrate Flutter gallery test to null safety (cla: yes, f: cupertino, f: material design, team)