NodeStatus API Endpoint for checking node health

[Kubuxu]

Initially, it would be used to confirm that node is in a good state before producing a message.

Checks proposed:

• the sync status: how far out of sync the node is.
  • Use the difference between the current time and genesis to figure out which epoch we should be at.
• peering status: do we have more than 5 peers with positive pubsub scores?
  • i.e. are we confident that if we send this message now, it will be properly propagated to the network?

[magik6k]

Maybe also some chain health metric, based on something like the number of blocks in last X epochs vs the expected number

[raulk]

Closed in #5767.