Move SkImageFilter over to storing sk_sps

This CL also removes the old bare-pointer style ctor.

GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1894573002

Review URL: https://codereview.chromium.org/1894573002
4 files changed