Add GPU index ID as a label like uuid

[winca]

I suggest adding the GPU index ID as a label, just like the GPU UUID. After all, for machines with multiple GPUs, it is easier to identify the corresponding GPU card through the GPU index ID.

[Soappyooo]

For people who want to query by index, this might help:

# query power draw of GPU with index 1
(0 * (nvidia_smi_index==1)) + on (uuid) group_left() nvidia_smi_power_draw_watts

# query power draw of GPUs, sort by index (use "Instant" type for Grafana)
(0 * sort(nvidia_smi_index)) + on (uuid) group_left() nvidia_smi_power_draw_watts