[analyzer] Add test for parser fix of bang question index
[analyzer] Add test for parser fix of bang question index

This is a follow-up to
https://dart-review.googlesource.com/c/sdk/+/141886 adding the
requested test to analyzer.

Change-Id: Ibb34886943b6a80c218212acad17b93b83faadb5
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/142999
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