Validate that all tests are passing for non-function type aliases prior to release.

[leafpetersen]

This issue tracks support of the non-function type alias feature. See the enclosing meta-issue for details.

cc @franklinyow @eernstg @mit-mit

[eernstg]

As of Feb 11 2021, https://dart-review.googlesource.com/c/sdk/+/184460 migrates all non-function type alias legacy tests to mixed-version tests where the non-function type aliases are declared in an opted-in library and the remaining code is in an opted-out library.

They are all passing, except language/nonfunction_type_aliases/mixed/aliased_cyclic_superclass_error_test.dart, whose failure occurs because test.py does not recognize the // ^, // [analyzer] .. error expectation syntax when it occurs in a non-entry-point library, cf. #44990.

[eernstg]

@leafpetersen, do you expect this check to be repeated up to the release event, or is it a one-shot validation? If it is the latter then I believe that we can close this.

[leafpetersen]

I'd like to leave this open until we're sure that we've landed all of the tests that we're going to land. I'm assuming we will need (at least) tests for the new cyclic typedef resolution rules?

[leafpetersen]

Also, this is intended to cover co19 tests as well, are those all passing?

[leafpetersen]

Looking good here, zero failing tests except the known bad co19 tests waiting a roll.