Replace GrResourceCache with GrResourceCache2.

BUG=skia:2889

Committed: https://skia.googlesource.com/skia/+/66a450f21a3da174b7eed89a1d5fc8591e8b6ee6

Committed: https://skia.googlesource.com/skia/+/407aa584d183c1bf314f5defd1cf0202e8a96c89

Review URL: https://codereview.chromium.org/716143004
SkDocument SK_API

Review URL: https://codereview.chromium.org/726073002
Make GrResourceCache2 responsible for calling release, abandon, and ~.

BUG=skia:2889

TBR=robertphillips@google.com

NOTRY=true

Review URL: https://codereview.chromium.org/729683002
Guard high water cache stats vars by GR_CACHE_STATS

TBR=halcanary@google.com
NOTRY=true

Review URL: https://codereview.chromium.org/729753003