False positive warning when serving dedicated memory allocations to small images

[haasn]

The best practices layer spits out warnings like this:

Allocating 4096 memory of type 0x1 (id 0) in heap 0
vk Validation Performance Warning: [ UNASSIGNED-BestPractices-vkAllocateMemory-small-allocation ] Object 0: handle = 0x55e896a0f0b0, type = VK_OBJECT_TYPE_DEVICE; | MessageID = 0xdc18ad6b | vkAllocateMemory(): Allocating a VkDeviceMemory of size 4096. This is a very small allocation (current threshold is 262144 bytes). You should make large allocations and sub-allocate from one large VkDeviceMemory.
    using VkDevice: anon (0x55e896a0f0b0)
vk Validation Performance Warning: [ UNASSIGNED-BestPractices-vkBindMemory-small-dedicated-allocation ] Object 0: handle = 0x55e896a0f0b0, type = VK_OBJECT_TYPE_DEVICE; | MessageID = 0xb3d4346b | vkBindImageMemory(): Trying to bind VkImage 0x157c000000157c[] to a memory block which is fully consumed by the image. The required size of the allocation is 4096, but smaller images like this should be sub-allocated from larger memory blocks. (Current threshold is 1048576 bytes.)
    using VkDevice: anon (0x55e896a0f0b0)
vk Validation Performance Warning: [ UNASSIGNED-BestPractices-vkAllocateMemory-small-allocation ] Object 0: handle = 0x55e896a0f0b0, type = VK_OBJECT_TYPE_DEVICE; | MessageID = 0xdc18ad6b | vkAllocateMemory(): Allocating a VkDeviceMemory of size 4096. This is a very small allocation (current threshold is 262144 bytes). You should make large allocations and sub-allocate from one large VkDeviceMemory.
    using VkDevice: anon (0x55e896a0f0b0)
Imported 4096 of memory from fd: 7 (dedicated)
vk Validation Performance Warning: [ UNASSIGNED-BestPractices-vkBindMemory-small-dedicated-allocation ] Object 0: handle = 0x55e896a0f0b0, type = VK_OBJECT_TYPE_DEVICE; | MessageID = 0xb3d4346b | vkBindImageMemory(): Trying to bind VkImage 0x157e000000157e[] to a memory block which is fully consumed by the image. The required size of the allocation is 4096, but smaller images like this should be sub-allocated from larger memory blocks. (Current threshold is 1048576 bytes.)
    using VkDevice: anon (0x55e896a0f0b0)

However, this is in spite of the fact that I am trying to serve memory to an image which has VkMemoryDedicatedRequirementsKHR.requiresDedicatedAllocation set to true, so there is no other way I could be allocating/binding memory here - no matter how wasteful it may seem to the layer. (Moreoever, one of the two allocations isn't even an allocation - it's a memory import from an FD, the size of which we have no control over)

I suggest adding a simple check to the best practices layer to disable those two VUIDs when serving images that require dedicated allocations.

[mark-lunarg]

@haasn, added this to the BP tracking issue #24, hoping to get to it soon. Thanks!