go/types, types2: move type recording functionality in its own files
This CL simply moves recording functions into recording.go and
adjust the imports as needed. There are no other code changes.
Preparation for generating go/types/recording.go from types2
sources.
Change-Id: Idc5850462a78afb1bfce78ba216722d07c8bca1e
Reviewed-on: https://go-review.googlesource.com/c/go/+/602116
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Robert Griesemer <gri@google.com> Reviewed-by: Robert Griesemer <gri@google.com> Reviewed-by: Tim King <taking@google.com>