[gpu] Add dawn vulkan allocator support for dumps and UMA

Support Graphite-Dawn-Vulkan allocator dumps to be reported as both
background and detailed reports. Also add a new prefix under
"gpu/vulkan" for graphite_allocator which will be used for reporting
the dumps. The same prefix is also used for reporting to UMAs so the
same Memory.Experimental.Gpu2.Vulkan UMA can be used for both
ganesh and graphite (since vma_allocator will only report for ganesh
and graphite_allocator only for graphite).

Bug: 397720827
Change-Id: Ie851c7c08cde4c5e2db0df220427c25263891f1e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6387675
Reviewed-by: Kyle Charbonneau <kylechar@chromium.org>
Reviewed-by: Vasiliy Telezhnikov <vasilyt@chromium.org>
Commit-Queue: Saifuddin Hitawala <hitawala@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1437919}