layers: Move and rename validate_descriptor_availability_in_pool
layers: Move and rename validate_descriptor_availability_in_pool

Signed-off-by: Chris Forbes <c3279c50043e18e9442c1ae071cafa0e7a4ca967@google.com>

Radamanthe/VulkanSamples,Radamanthe/VulkanSamples,Radamanthe/VulkanSamples,Radamanthe/VulkanSamples,Radamanthe/VulkanSamples,Radamanthe/VulkanSamples