Add support for multiple harvesters/farmers in Grafana dashboard and prometheus scrape config

[sbates130272]

Right now we can run the chia-exporter on multiple machines but there is no example prometheus or Grafana code to either view the data on each machine or add up stats (like plots) across all machines. Can we look at adding this?

[speedmann]

I unfortunately only have one system i can monitor at the moment.
But for this to work it should be possible to decide which node types to export. I'm thinking about some more variable types like MONITOR_HARVESTER MONITOR_FULL_NODE or something simmilar.
But, as said, to develop this i will need an additional node for which i currently do not have any resources available

A PR would be welcomed if you have the possibility to do so