proposal: go/types: provide types.Satisfies predicate

[griesemer]

With the acceptance of #56548, there's a difference between interface implementation and constraint satisfaction; the latter makes an exception with respect to comparability of types (see #56548).

Since we can't add a flag to types.Implements (breaks backward compatibility), the proposal is to add a new predicate:

// Satisfies reports whether type V satisfies the constraint T.
//
// The behavior of Satisfies is unspecified if V is Typ[Invalid] or an uninstantiated
// generic type.
func Implements(V Type, T *Interface) bool

cc: @findleyr

[griesemer]

Closing again as partial duplicate of #56548. I missed that I already made this API addition part of #56548.