go/types, types2: factor out typechecker-specific code from recording.go
With this CL, the go/types and types2 recording.go files are
mostly identical except for the use of different syntax trees.
Preparation for generating go/types/recording.go from types2
sources.
Change-Id: Iea85f8554ee04f1e1f7da63f8019725ac8f6caf5
Reviewed-on: https://go-review.googlesource.com/c/go/+/602117 Reviewed-by: Tim King <taking@google.com> Reviewed-by: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>