[ETCM-48] Add json rpc http healthcheck

[mirkoAlic]

Description

This healthcheck functionality needs to be back ported from the other project, given is needed for testnet cluster purposes.

How to test

Manually run the node and use:

curl --request GET \
  --url http://127.0.0.1:8546/healthcheck \
  --header 'cache-control: no-cache'

Expected response

{
  "checks": [
    {
      "description": "listening",
      "status": "OK"
    },
    {
      "description": "peerCount",
      "status": "OK"
    },
    {
      "description": "earliestBlock",
      "status": "OK"
    },
    {
      "description": "latestBlock",
      "status": "OK"
    },
    {
      "description": "pendingBlock",
      "status": "OK"
    }
  ]
}

[mmrozek]

Do we have any tests for failing healthcheck scenario?
Apart from that LGTM!

[mirkoAlic]

Do we have any tests for failing healthcheck scenario?
Apart from that LGTM!

There is no tests for healthcheck at all. As this is required with some rush, i will add some in a future PR.