clean up unused SkVM debug features

I'm not using any of these, so nice to move them aside.

Change-Id: Id43c1606c2f9e6bba0d8f6bd7d2f8f5e02d5b762
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/338629
Auto-Submit: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Mike Reed <reed@google.com>
4 files changed