cmd/compile: update types2.Info.FileVersions API to match go/types

cmd/compile: update types2.Info.FileVersions API to match go/types

This CL changes the FileVersions map to map to version strings
rather than Version structs, for use with the new go/versions
package.

Adjust the cmd/dist bootstrap package list to include go/version.

Adjust the compiler's noder to work with the new API.

For #62605.
For #63974.

Change-Id: I191a7015ba3fb61c646e9f9d3c3dbafc9653ccb5
Reviewed-on: https://go-review.googlesource.com/c/go/+/541296
Reviewed-by: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Robert Griesemer <gri@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>