* wip run_local_linter.dart

* get run_local_linter.dart working

* slow working implementation

* speed up run_local_linter.dart

* fix run_local_linter.dart

* remove catchError

* another fix

* fix another

* fix

* more fixes

* fix moar

* fix moar

* fix

* finish

* fix tests

* clean up further

* code review

* delete run_local_linter.dart

This modifies the flutter update-packages and flutter update-packages --force-upgrade commands so that the many invocations of "dart pub get" in each repo project run in parallel instead of in series.