Extended VmaAllocationInfo to include the size of the actual allocation

[debaetsd]

Extended VmaAllocationInfo to include the actual allocation size (as-in the size used to allocate the memory when calling VkAllocateMemory).

We need the size when performing interop between Vulkan and OpenGL.
glImportMemoryFdEXT requires the size of the actual underlying Vulkan object to be passed in (not the size of a suballocated resource).

We worked around it by using dedicated allocations though extending VMA to query the size of the underlying allocation allows the benefits of the block allocator.

[adam-sawicki-a]

Thank you for reporting this issue. I am sorry but I don't want to merge it. Query for VmaAllocationInfo is a function that may be called very often, so I want to keep it fast and avoid growing it in scope, while returning the size of the underlying memory block looks to me like an exotic feature.

Please feel free to maintain your fork of the code with this change. Another option could be using dedicated allocations or custom pools with specific VmaPoolCreateInfo::blockSize so that the size is known.

I also suggest to rename the new parameter, as "allocation" is used in VMA to name a single sub-allocated region of a memory block, as in VmaAllocation, so I recommend to rather call it a "block", "memory block", or "Vulkan memory" size.