Passes the Piglit test nv_conditional_render-vertex_array.
WIP as flushing, long range (across FBO binds) and non-draw functions such as Clear and DispatchCompute are not handled yet. The simplest option would be to just be to wait for the query to complete and decide whether to do anything CPU-side.
Enables OpenGL 3.0 by default on t760+:
$ PAN_MESA_DEBUG= glxinfo | grep "GL version" OpenGL version string: 3.0 Mesa 20.3.0-devel