feature: dynamic job names

[benv666]

I've added two variables, for the eth2 and validator job selectors.
This allows users such as me that already run external monitoring to easily adapt the dashboard to their setup.
(in my instance I have a central prometheus that scrapes several items on my node, by changing the job name I can make the dashboard functional without having to jump through hoops)

These variables will be prompted and can be changed during import:

Feedback welcome.

[jclapis]

Can you put the old v1.3.0 dashboard file back in instead of removing it post-rename? I can approve this for the next dashboard but don't want to clobber the current v1.3.0 source.

[benv666]

Accidental close there, I've reverted the 1.3.0 file and added 1.3.1 with a third variable to also make the eth1 job name dynamic.
While this works for the eth1 job, I did note there's a hardcoded geth in a few spots - not sure if that's by design since I'm not running it like that.

[jclapis]

Accidental close there, I've reverted the 1.3.0 file and added 1.3.1 with a third variable to also make the eth1 job name dynamic. While this works for the eth1 job, I did note there's a hardcoded geth in a few spots - not sure if that's by design since I'm not running it like that.

It is by design because Geth has a different metrics path than Besu and Nethermind; due to that, geth is for Geth, eth1 is for Besu and Nethermind. I couldn't find a way to have one Prometheus job scrape multiple endpoints, so we'd have to make it an envsubst variable. Unfortunately, that requires knowing which EC is selected at all times (and the Smartnode doesn't know what's selected for hybrid mode).