v3d: Replace the old shader-db env var output with the ARB_debug_output.

v3d: Replace the old shader-db env var output with the ARB_debug_output.

We're using ARB_debug_output for the main shader-db, but I had this env
var left around from the shader-db-2 support (vc4 apitrace-based).  Keep
the env var around since it's nice sometimes to get the stats on a shader
you're optimizing without having to do a shader-db run, but drop the old
formatting that's not useful and keeps tricking me when I go to add
another measurement to the shader-db output.