79908 Start migrating flutter_tools test src to null safety (a: null-safety, cla: yes, team, tool, waiting for tree to go green)

79913 add new try/prod builders for validate_ci_config (cla: yes, team, waiting for tree to go green)

79917 Allow null Config.getValue() results (a: null-safety, cla: yes, team, tool)

79959 Unblock roll by reverting #79061 (a: tests, cla: yes, framework, team)

79961 Mark integration_test_test as unflaky (cla: yes, team, waiting for tree to go green)

tool - 346 pull request(s)

61221 [flutter_tools] Add ARM64 Linux host and cross-building option support (a: desktop, cla: yes, platform-linux, tool)