Extract Vulkan methods out of GrBackendSemaphore

This is a necessary step towards making the Vulkan backend
modular and Bazel-friendly.

Change-Id: I245cbab55d3c11870414c434432c85798fd6a6a5
Bug: b/293490566
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/781236
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>
14 files changed