[packages] Run autoformat as part of min-SDK update

[stuartmorgan-g]

The Dart formatter behavior is now min-Dart-SDK dependent, so running a mass min SDK update requires running dart pub get and then the formatter to avoid potential CI failures on the autoformat check. It's easy to forget to run format, and even easier to forget to dart pub get (and there's no obvious way to mass-run the latter in the tool), so when running a min-SDK update we should (maybe with a flag to suppress it) run the pub get and Dart format steps automatically on any package where the min SDK actually changed, instead of making it something the caller has to deal with.