Add a VkMemoryDedicatedAllocateInfo to the vkAllocateMemory pNext chain
if the client specifies the memory object was a dedicated allocation.

We don't yet support suballocation of external memory objects, so all
allocations are already effectively dedicated allocations regardless
of whether vulkan requires it.

The spec requires that memory passed to vkBindImageMemory be created with
a VkMemoryDedicatedAllocateInfo if the driver requires dedicated
allocations for that VkImage. If the driver does not require a dedicated
allocation, there actually seems to be no explicit requirement to use
this structure even if it was passed in at allocation time.

Bug: angleproject:4627
Change-Id: I8a660e871bdf72815815f0c0b3000f3b0570bd2d
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2192501Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Michael Spang <spang@chromium.org>