device_memory_report: key resources by object type, emit object_type, clamp bindings

[jimblacklercorp]

Two commits:

device_memory_report: key resources by object type and emit object_type on allocation events

VkBuffer and VkImage handles are only unique within their object type,
but resources_ and resource_to_memory_map_ were keyed by bare handle. A
buffer and an image sharing a handle value could overwrite each other's
usage, size and binding, and a binding's DESTROY source was derived from
whichever resource last claimed the handle.

• Key resources_ by ObjectKey (std::pair<VkObjectType, uint64_t>, the
  same key as debug_object_names_) and store the object type on
  SubAllocation.
• Fold resource_to_memory_map_ into Resource::bound_memory so the
  binding lives with the resource it describes.
• OnRecordResourceSize and GetRecordedResourceSize take the object type.
• Emit an object_type (VkObjectType) annotation on every
  VulkanMemoryAllocation event: VK_OBJECT_TYPE_DEVICE_MEMORY for memory
  blocks, VK_OBJECT_TYPE_BUFFER / VK_OBJECT_TYPE_IMAGE for bindings, and
  the driver-reported objectType for driver allocations, so consumers
  can key allocations and join debug names without inferring the type.
• Add BufferAndImageWithCollidingHandlesAreTrackedIndependently test.

device_memory_report: clamp bindings to their allocation in the unbound counter

UpdateAllocationUnboundCounter merged each binding's [offset,
offset + size) interval without regard to the allocation's bounds, so a
binding that extended past the end of its VkDeviceMemory counted bytes
outside the allocation as bound, and unbound_memory under-reported.

Clamp each interval to [0, total_size) when the counter is computed, so
only the part of a binding inside the allocation counts as bound.
Clamping at compute time rather than bind time keeps bindings recorded
against a not-yet-reported allocation correct once its size arrives.
bound_size can then no longer exceed total_size, so the unbound
subtraction needs no guard. This matches the Sherlock snapshot, which
clamps the same way.

• Add BindingsAreClampedToTheirAllocation test.