Remove hasMixedSamples() from GrPipelineBuilder

This info is unknown until after any clip has been applied to the
stencil settings, so it's misleading to include in the builder.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1952323002

Review-Url: https://codereview.chromium.org/1952323002
14 files changed