Not removing from any file with a language marker.
Also not touching anything in `tests/language/primary_constructors`
or `.../private_named_parameters`, which are both assumed to be
primary constructor feature aware.
Two files rewritten from multi-test to error-test.
Change-Id: I43d444a35a41c7734f266794e9f167655692473f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/480640
Reviewed-by: Nate Bosch <nbosch@google.com>
Commit-Queue: Lasse Nielsen <lrn@google.com>