Various dart fixes

[fundthmcalculus]

This is bunch of minor things I've found as part of building the Dart services SDK.

[geel9]

This and a few other recent PRs across the org have been very difficult to review due to a huge amount of files changed solely for style / formatting reasons.

We should have a conversation to figure out a way to keep PRs sane when large formatting changes are at play.

[fundthmcalculus]

This and a few other recent PRs across the org have been very difficult to review due to a huge amount of files changed solely for style / formatting reasons.

We should have a conversation to figure out a way to keep PRs sane when large formatting changes are at play.

Yup, in the future, this won't be such an issue. I've been working (very casually in okapi repo) to add coding style checkers. Since Dart isn't officially supported, I wasn't worried about style PRs yet. Also, this PR moves to using dart format.

opens can of worms about style guidelines