86378 Migrate devicelab tasks f-i to null safety. (team, a: accessibility, cla: yes, a: null-safety)

86386 Revert “Clean up the bindings APIs” (a: tests, team, framework, f: material design, a: accessibility, cla: yes, f: cupertino, d: examples)

86388 Clean up the bindings APIs (a: tests, team, framework, f: material design, a: accessibility, cla: yes, f: cupertino, d: examples, waiting for tree to go green)

86392 Fixed a cast issue with host_mode_tests.dart. (team, cla: yes)

86393 Always write devicelab test results to a file if the resultsPath option is present (team, cla: yes, waiting for tree to go green, team: infra)