Migrate CopyConstants out of RP utils.

Nothing is landed which actually uses this yet, so it's a pretty
simple CL.

Change-Id: Ic285a4079d29af0ed02d61aab7ccd6a3e85223ae
Bug: skia:13676
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/620841
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
5 files changed