[Vulkan] Region allocator fixes for memory requirements and allocations

[derek-gerstmann]

As reported by #8079

• Add region allocator tests that check alignment, nearest_multiple and collect routines
• Fix can_split() routine to use conformed sizes so that split allocation matches
• Fix region size accounting so that coalesce never has zero size regions to merge
• Fix aligned_offset() routine to check for zero alignment (which means no constraint)
• Use Vulkan memory_requirements to determine nearest_multiple during initialization
• Query Vulkan memory_requirements for each region, and reallocate if driver requires additional device memory

[steven-johnson]

LGTM.

As a nit, there were a lot of superficial changes in debug output that made it harder to parse out the functional changes for review.

[derek-gerstmann]

LGTM.

As a nit, there were a lot of superficial changes in debug output that made it harder to parse out the functional changes for review.

Yes, sorry. I tried to isolate the debug formatting stuff to separate commits.

[steven-johnson]

Ready to land?

[derek-gerstmann]

Yes, this one is done. There will be more fixes soon.