Print the type parameter bounds of higher kinded types

[adpi2]

Fix #13306

When the exported type is a higher-kinded type, we print the bounds of its type parameters.

Co-authored by @bishabosha
Co-authored by @mlachkar

[adpi2]

This PR changes the error reporting of unchecked type bounds as in i11637:

object test2:
  class FunctorImpl[Generic1[T] <: Iterable[T]]{}
  class HKT3_1[Functor[Generic2[T<:String]<:Set[T]]]{}
  var h = new HKT3_1[FunctorImpl]();  // error // error

[E057] Type Mismatch Error: tests/neg-custom-args/i11637.scala:11:21 ------------------------------------------------
11 |  var h = new HKT3_1[FunctorImpl]();  // error // error
   |                     ^
-   |                 Type argument test2.FunctorImpl does not conform to upper bound [Generic2[T] <: Set[T]] =>> Any
+   |       Type argument test2.FunctorImpl does not conform to upper bound [Generic2[T <: String] <: Set[T]] =>> Any

I updated the check file because the new message looks more accurate.

[bishabosha]

i noticed the lower bound does not print either, implying it's Nothing, however it is still inconsistent with how a TypeBoundsTree is printed - if you look at the original MyType - but that would lead to very verbose error messages I think.

One solution could be some print mode parameter which knows if we are printing "full trees" or just the type, which could allow you to decide when to always print the lower bound

[odersky]

Looks good to me.