[be] Reorganize logging dir

[xuzhao9]

Organize the logging directory. Now log to /tmp/tritonbench_$USER_$LOGGING_GROUP/$BENCHMARK_NAME/$BACKEND_$INPUT_XVAL/$METRIC.<extension>.

Fixes #94

Test plan:

$ python run.py --op softmax --only triton_softmax --num-inputs 1 --metrics kineto_trace,ncu_rep
  x_val                           triton_softmax-kineto_trace                                                triton_softmax-ncu_rep
-------  ----------------------------------------------------  --------------------------------------------------------------------
 2176.0  /tmp/tritonbench_xzhao9/softmax_fwd/triton_softmax_0  /tmp/tritonbench_xzhao9/softmax_fwd/triton_softmax_0/ncu_rep.ncu-rep

$ tree -L 3 /tmp/tritonbench_xzhao9/
/tmp/tritonbench_xzhao9/
└── softmax_fwd
    └── triton_softmax_0
        ├── devvm3059.eag0.facebook.com_1351975.1752690766606139153.pt.trace.json
        ├── devvm3059.eag0.facebook.com_1357864.1752690851550292231.pt.trace.json
        ├── devvm3059.eag0.facebook.com_1358481.1752690861764172111.pt.trace.json
        ├── devvm3059.eag0.facebook.com_1376058.1752691079417859893.pt.trace.json
        └── ncu_rep.ncu-rep

2 directories, 5 files

[FindHao]

LGTM!
nit: can you add a Test Plan? maybe use tree -L 2 to show the output folder structure?

[xuzhao9]

Addressed comments.