cmd/compile, go/types: allow `any` anywhere (as a type)

cmd/compile, go/types: allow `any` anywhere (as a type)

Adjust types2 and go/types and some test cases.

Because `any` is not treated specially anymore in constraint
position we get additional errors in constraints if `any` is
used before Go1.18 (in addition to the error that type parameter
lists are not permitted before Go1.18).

Fixes #33232.

Change-Id: I85590c6094b07c3e494fef319e3a38d0217cf6f0
Reviewed-on: https://go-review.googlesource.com/c/go/+/351456
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>