tests: GH421 vkUpdateDescriptorSets tests

tests: GH421 vkUpdateDescriptorSets tests

A) Adding the WriteDescriptorSetIntegrityCheck test, which verifies
some requirements of chapter 13.2.3 of the Vulkan Spec
 1) A uniform buffer update must have a valid buffer index.
 2) When using an array of descriptors in a single WriteDescriptor,
      the descriptor types and stageflags must all be the same.
 3) Immutable Sampler state must match across descriptors
The above tests also exercise cases where descriptors are updated with
consecutive bindings both correctly and incorrectly

B) adding a MissingClearAttachment test that points to a wrong
colorAttachment index in a VkClearAttachment structure passed to
vkCmdClearAttachments

C) update vk_validation_layer_details.md to reflect above changes.

Change-Id: I3f4f2233371b68caf23b5a4111d63a94765121c3