Add rename migrations for all the screaming snake case constants that
were renamed to lower camel case during the Dart 2 migraiton.
Rename the test from `file.dart` to `io.dart` so that we can test all
deprecations for the same import together. Add a test for the same
deprecations when imported through `dart:html`.
Change-Id: Iee91d88b1b11648e8c65cfcc8d2fcfabac3954ec
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/203820
Auto-Submit: Nate Bosch <nbosch@google.com>
Commit-Queue: Phil Quitslund <pquitslund@google.com>
Reviewed-by: Lasse R.H. Nielsen <lrn@google.com>
Reviewed-by: Phil Quitslund <pquitslund@google.com>
Nate Bosch