UAV counter descriptors are stored in a separate VkDescriptorSet.
A VkPipelineLayout created for compute pipeline is compatible for all
other descriptor sets with the VkPipelineLayout created for the root
signature. This ensures that only UAV counter bindings in the last
descriptor set may be disturbed when switching between pipelines with
compatible root signatures.
The implementation of vkd3d_popcount() is based on
https://graphics.stanford.edu/~seander/bithacks.html
