Adjust monitor-net settings

[frenchu]

Assigning a static address for monitor-net can lead to an issue. User can run other compose projects and create custom networks. By default docker will assign random network addresses automatically. When user already has a docker network with the same address as monitor-net address, rocketpool services are not starting:

 ✘ Network rocketpool_monitor-net Error 0.0s
failed to create network rocketpool_monitor-net: Error response from daemon: cannot create network b5fe819f2eb9d83d916309fcacde43fc22a08368ab9f083be13ac9e0baaa5891 (br-b5fe819f2eb9): conflicts with network dff50a78ca4140c6ccef48a845397cbea6a38833bb1b35f4b68bd6777dd4bd7f (br-dff50a78ca41): networks have overlapping IPv4
exit status 1

Moreover, Grafana service can be isolated from containers in rocketpool_net and connected to monitor-net with Prometheus service.

More details in the pull request comments.

[frenchu]

Run Grafana service in monitor-net for better network isolation.

[frenchu]

The stackoverflow solution refered in the comment is obselete by now. Adding "host.docker.internal:host-gateway" as an extra host is enough alone. The stackoverflow answer was updated to reflect that.

[frenchu]

The RocketPool docs don't assume any particular network address for monitoring, so docker compose can assign network address for monitor-net by itself. The network address should not change later during RP node operation, since the networks are not recreated on starting/stopping RocketPool services. For current node operators the address will also not change.