asahi: Implement occlusion queries

asahi: Implement occlusion queries

While the hardware supports both counter and boolean occlusion queries, the
programming model is quite different from OpenGL. In AGX (and in Metal),
there is a single "visibility result buffer" associated with the render pass.
Each draw that uses occlusion queries writes into this render pass global
visibility result buffer at a particular index. By contrast, the OpenGL
occlusion query model supposes that each query has independent state that can be
mixed and matched within a render pass. We can't simply allocate backing memory
for a query and write to it from a job. We can't allocate visibility result
buffers for each batch up front and statically assign OpenGL queries to indices,
because the OpenGL query can span multiple batches. Finally we can't use a
global visibility result buffer without introducing additional synchronization,
given that we now support multiple batches in-flight at once.

In this patch, I've elected to use a simple solution: allocate visibility result
buffers and indices on the fly as needed, and accumulate the results on the CPU
at the end of the render pass. When we have proper synchronization we'll want to
revisit this, but as everything is stalling at submit time now, I'm not inclined
to "optimize" something I can't test.

Passes dEQP-GLES3.functional.occlusion_query.* and the relevant piglit tests.
The piglits are considerably more thorough, checking lots of "we hate tilers"
conditions that dEQP skips over.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20123>