remove 'deprecated' region from SkDraw

Most call-sites that used it just took its bounds, so it was trivial to convert them
to get the bounds of the RasterClip. Two clients wanted the actual region:
1. layeriter for android
2. pdf

Android already only has BW clips, so should be safe.
PDF now overrides its clip methods to ensure that all clips are BW.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1925693002

Review URL: https://codereview.chromium.org/1925693002
20 files changed