[CMSR] Tests for removing first / last named / positional formal parameter.

Change-Id: I4028f17b9244835beb60d955f12763ff9184afc4
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/310967
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

https://dart.googlesource.com/sdk/+/c2ffa07d7e7f1448b927d460acb0980067cbda2e