Replace targetHasUnifiedMultisampling in GrPB constructor

Replaces targetHasUnifiedMultisampling with a simpler "useHWAA". Now
the code that creates a pipeline builder needs to decide on its own
whether it should enable multisampling, rather than relying on the
builder to try and guess.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2041283002

Review-Url: https://codereview.chromium.org/2041283002
19 files changed