implement a consensus layer proxy solution

[cjorge-graphops]

We need a proxy/load-balancer for at least ethereum consensus layer for HA.

Immediate use-case would be arbitrum, as since arbitrum-nitro v3 (graphops/launchpad-charts@8fcfc77) it now requires a beacon endpoint.

This could be done maybe in a very hackish way like for Heimdall in polygon with the combo of an ad-hoc SVC + health-check, or we should consider this: https://github.com/ethpandaops/dugtrio . One challenge there is that it's not-obvious if that proxy itself can scale to multiple replicas running (the helm chart fixes replicas to 1).