Nanobench running on Vulkan

This lets nanobench run but the timings are inaccurate because of missing
implementations of synchronization functions in VkTestContext.

GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1965273004

Review-Url: https://codereview.chromium.org/1965273004
6 files changed