bench, samples, etc: s/SkAutoTUnref/sk_sp/

bench, samples, etc: s/SkAutoTUnref/sk_sp/

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4437

Change-Id: Ice071684ac8a99e4bb405b4b9be8e8f42c7bac42
Reviewed-on: https://skia-review.googlesource.com/4437
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Hal Canary <halcanary@google.com>