dzn: Add support for queries

I wish the implementation was simpler, but unfortunately, the vulkan and d3d12 query APIs are quite different:

• vulkan users can get query results outside the command buffer
• vulkan allows query begin/end and copy-results to be in different command buffers, thus forcing us to keep track of the query state
• vulkan has the concept of availability which is an extra word encoding whether the results are valid or not
• vulkan API allows the use to provide a stride along the result buffer
• vulkan API allows non-blocking result retrieval

All these differences force us to keep track of the query state and do extra copies.

based on !49 (merged)

/cc @lfrb