GET /node/* - Implement Node endpoints

[rodrigo-o]

Implement the Node endpoints of the Beacon API, this could become an umbrella task pointing to smaller task for each individual endpoint. for now this is just to track the progress in the Node endpoints implementation:

• eth/v1/node/identity
• eth/v1/node/peers
• eth/v1/node/peers/{peer_id}
• eth/v1/node/peer_count
• eth/v1/node/version
• eth/v1/node/syncing
  • semi-stub implementation.
• eth/v1/node/health
  • semi-stub implementation

Ref: https://ethereum.github.io/beacon-APIs/#/Node