Add simple status check for node to backend

[diamondhands0]

An endpoint that allows our validator hub to quickly tell you if your node is reachable by other validators.

Curl command to test it, assuming you're running backend on 18001 and a real node on 18000 (eg like we do with n0_test).

$ curl 'http://localhost:18001/api/v0/check-node-status'  -H 'content-type: application/json'  --data-raw '{"NodeHostPort":"localhost:18000"}'   --compressed

When successful returns:

{"Success":true}

When not successful returns:

{"error":"Problem connecting to dorsey.bitclout.com:18002: dial tcp 35.192.117.201:18002: i/o timeout"}

{"error":"Problem connecting to localhost:18003: dial tcp 127.0.0.1:18003: connect: connection refused"}