go/types, types2: substitution crashes when GODEBUG=gotypesalias=1 and alias types occur in generic types #65854
Description
Test case:
// -gotypesalias=1
package p
type A = int
type T[P any] *A
var _ T[int]{{ message }}
Test case:
// -gotypesalias=1
package p
type A = int
type T[P any] *A
var _ T[int]