[graphite] Add VulkanDescriptorPool, VulkanDescriptorSet classes
* Adds the beginnings of wrapper classes around raw VkDescriptorPools and VkDescriptorSets
* Have descriptor sets add a ref to their originating descriptor pool handle such that a pool will not be freed if a descriptor set is still needed from that pool
* Adds a graphite-wide accessible header file which defines the types of descriptors graphite supports (Descriptors enum)
Change-Id: Ieb63f86987bef6a891fcb8fa4520cb16f08b564c
Bug: b/274762860
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/689076
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Nicolette Prevost <nicolettep@google.com>
5 files changed
