Use NVML except Xnvctrl in Wayland

[QkiZMR]

Recently, I switched to Wayland. The Nvidia graphs (gfx load, memory usage) that I have in Conky config stopped working. I had a similar problem with MangoHud on Wayland, but I needed to compile MangoHud with the NVML option enabled, and now it detects Nvidia gfx properly.

The question is: can Conky use the same NVML mechanism to get metrics from the NVidia card?

[Caellian]

Let's keep the discussion in #1615, I'll reopen it as it's older and has more context.