Rename SkAutoSTMalloc -> AutoSTMalloc move to skia_private

Add a catchall SkAutoSTMalloc to be removed when all the clients
have removed their uses.

Change-Id: I772fadece2500a9338ada346db17887de6946f19
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/628058
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Kevin Lubick <kjlubick@google.com>
37 files changed