DAL/Node: Add a way to get reconnection delays from Gossipsub worker

Useful when debugging!

How to test

make octez-dal-node
./octez-dal-node run --endpoint https://rpc.ghostnet.teztnets.com --observer 30

then on another terminal observe the output with:

./octez-client --endpoint http://127.0.0.1:10732 rpc get /p2p/gossipsub/reconnections

like:

[ { "point": "34.65.101.2:11732", "delay": "1min57s" },
  { "point": "34.124.127.111:11732", "delay": "1min57s" },
  { "point": "35.233.80.180:11732", "delay": "1min57s" },
  { "point": "46.137.127.32:11732", "delay": "1min57s" },
  { "point": "52.31.26.230:11732", "delay": "1min57s" } ]

(you may observe negative spans meaning that it can be recontacted now and the delta provides the first time this point could have been recontacted)