zink: print shaderdb info via debug message callback
shaderdb expects to receive shader info via a glDebugMessageCallback
callback. This patch updates print_pipeline_stats to use the zink_context::dbg
callback.
The format of the shader info is also updated to match what the shaderdb report.py script expects. In particular, we use what report.py calls "nv_format" since that is the closest to the current format.