Add support for getting vulkan descriptor sets without a GrVkUniformHandler.

This change allows us to use the current descriptor set system for doing
copies as draws. This is a step towards being able to track resources for draws
that don't go through out normal pipeline.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2275633002

Review-Url: https://codereview.chromium.org/2275633002
4 files changed