[Consistency] Rename --vcgencmd argument to --collector.gpu.vcgencmd

[ToMe25]

I believe the --vcgencmd argument should be renamed to --collector.gpu.vcgencmd or --collector.gpu.vcgencmd-path to be consistent with the node exporter argument naming scheme, which this collector seems to use.

This is because the vcgencmd command is only used for the gpu exporter, and thus not really a general config option.

The big issue with this is, however, that doing so would be a breaking change.

[lukasmalkmus]

Feel free to tackle this. I'll keep the issues open. But at the moment I don't have capacity to work in this exporter apart from occasional maintenance.

[ToMe25]

I opened these recent issues mostly to track these things, I don't consider them to have any significant urgency.

I will look into implementing some of them if and when I find the time and motivation to do so :)