Analyzer does not check that bounds are satisfied by generic metadata arguments

[leafpetersen]

The following example should be an error, since String is an invalid type argument for the generic class Y:

class Y<T extends num> {
  const Y();
}

@Y<String>()

class Test1 {}

The analyzer currently issues no errors on this code when run with --experiment=generic-metadata.

This is tests by co19/src/Language/Metadata/syntax_t11.dart, but unfortunately that test is broken pending the next co19 roll.

cc @devoncarew @scheglov @natebosch

[scheglov]

https://dart-review.googlesource.com/c/sdk/+/194000