[nnbd_migration] Do basic categorization of edit types to suppress noise.
[nnbd_migration] Do basic categorization of edit types to suppress noise.

We really should switch this, if possible, to use the edit kind APIs
that the preview tool uses, so that we can categorize this without
guesswork.

However this will keep it as a rough list, and I don't know if we need
anything fancier that currently -- and it will no longer produce noise
if new changes are added.

(currently produces "and 0 other changes" when running on flutter, so
it's probably mostly comprehensive currently).

Change-Id: I9cb2662995af340346a61d38eba3469927a0f4ef
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/145160
Reviewed-by: Paul Berry <72d414e3a99fb120308437779d51667bcc0984eb@google.com>
Reviewed-by: Mike Fairhurst <2002604e76601be549134505841fea93de80dc45@google.com>
Commit-Queue: Mike Fairhurst <2002604e76601be549134505841fea93de80dc45@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk