Begin removing deprecated (and now, unused) ImageFilter code paths

This CL focuses on removing the Proxy objects but takes some other stuff with it.

BUG=skia:4965
TBR=reed@google.com

GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1896383003

Review URL: https://codereview.chromium.org/1896383003
24 files changed