When -trimpath is used, packages built from the module cache still
have debug into that contains the module path and version. Only the
module cache directory is stripped.

With this CL, we now include the module path and version in the cache
key for build actions.

Fixes #35412

Change-Id: I1956592d0d86fcea2cca7c5fc8957e83543d6aa2
Reviewed-on: https://go-review.googlesource.com/c/go/+/207317
Run-TryBot: Jay Conrod <jayconrod@google.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>