radv: improve GPU hang report and replace RADV_TRACE_FILE by RADV_DEBUG=hang
Instead of printing various stuff to stderr/stdout, the driver now creates a directory into HOME/radv_dumps_
pid if a GPU hang is detected and it dumps logs. This also adds UMR GFX ring/waves dumps.
The main change for users is that RADV_TRACE_FILE is deprecated and replaced by RADV_DEBUG=hang, the famous trace file will be dumped to HOME/radv_dumps_
pid/trace.log.