21937 Roll the process_runner package used by the formatter script (cla: yes)

21938 Roll Dart SDK from b58cfe5ab24e to aaab579579be (1 revision) (cla: yes, waiting for tree to go green)

21939 [web] Fix image gap due to svg element without position attribute (cla: yes)

21940 Reformat some files that were not auto-formatted (cla: yes, platform-android, waiting for tree to go green)

21941 Add FML_UNREACHABLE to declare points in code that should never be reached. (cla: yes, waiting for tree to go green)

21942 [null-safety] fix type declaration of Picutre._toImage (cla: yes)