cmd/compile: handle `any` as alias like `byte` and `rune`

`types.Types[types.TINTER]` is already used for `interface{}`, so we
can conveniently just extend the existing logic that substitutes
`byte` and `rune` with `uint8` and `int32` to also substitute `any`.

Fixes #49665.

Change-Id: I1ab1954699934150aab899b35037d5611c8ca47e
Reviewed-on: https://go-review.googlesource.com/c/go/+/365354


Trust: Matthew Dempsky <mdempsky@google.com>
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>