vulkan: refactor interop API

I want to deprecate the clumsily designed pl_sync / pl_tex_export APIs, and instead merge this functionality (which is extremely Vulkan-specific) into the pl_vulkan_hold/release helpers. This requires doing a number of things:

1. Minor internal refactoring to support arbitrary queue family transitions
2. Generalize/expand pl_vulkan_hold and pl_vulkan_release to add uint32_t qf parameters
3. Create a helper for creating vulkan-specific (exportable) semaphore objects, replacing the old pl_sync abstraction