Add Beacon Node proxy for Proof of Stake

[mohamedmansour]

Right now we listen on each node from the execution client for Proof of Work to get the metadata, and we do some stats to get the data you see today. Since Proof of Stake will come soon, we need to get ready and listen on the beacon node to get the data as well. We need a plan to implement that.

Perhaps the tasks would be broken up by:

• Create a few Docker images that host an PoS Executor Node, and Beacon Node, on Kitsugi testnet. We need this to upgrade to more beefier system.
• Implement a Golang client that connects to either Prysm Beacon or Lighthouse Beacon.
• Create interface wrappers around the current PoW and PoS to gather similar metrics.
• Update the stats.go and hub.go to use the new wrappers.
• Update the React frontend to allow us to switch to testnet (we had previous code that does that)
• Bring back the old countdown for testnet!