Elements. Un-comment ClassElementTest_augmentation, but skip each test method.

I will start looking at individual methods and try to make them work.

Change-Id: Ied545392f324f035d72bf8e2d954fa9b1ded0cf7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/442250
Reviewed-by: Samuel Rawlins <[email protected]>
Commit-Queue: Konstantin Shcheglov <[email protected]>

Author: scheglov