[analyzer] Add test for bang before type arguments
[analyzer] Add test for bang before type arguments

In https://dart-review.googlesource.com/c/sdk/+/128402 I was asked to
add a test to the analyzer.
This is the (somewhat belated) follow-up that does that.

Change-Id: I7065882b458a480b12d79a4913a59e2bee4f35da
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/136184
Reviewed-by: Brian Wilkerson <1f7641b6b14c52b9163524ab8d9aabff80176f21@google.com>
Commit-Queue: Jens Johansen <05223a3c6bdf76af6f84755eae231abeebcf4530@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