Use AMD Vulkan Memory Allocator for device memory sub-allocation.
We now have a mempool from which all glBuffer memory is allocated.
The CPU overhead involved in repeated IOCTL calls to the kernel is
reduced significantly.

Bug: angleproject:2162
Change-Id: Id7681ffe2ac3d2853141ebe34c7df7b7fdd0d55e
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2124519Reviewed-by: Tobin Ehlis <tobine@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Mohan Maiya <m.maiya@samsung.com>