Split VulkanTestHelper out into its own files

The aim here is to unify VkTestHelper with the VkYcbcrSamplerHelper's context creation code. AFAICT they have a ~90% overlap.

Change-Id: Iba8d1482b8c1d7164682f90e19d2183d8cfe45d4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/295583
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
4 files changed