Validate highest Bitcoin block after Chainhook node restart

[csgui]

When a Chainhook node is restarted, it appears to lose the Bitcoin node state. This can cause issues, like the one below, to be triggered by Grafana.

The Chainhook node <NODE_NAME> is (852343) Bitcoin block(s) behind chain tip

Chainhook should retain the highest Bitcoin block received for a while.

A simple investigation can be conducted here. Here are the steps involved:

1. Restart a Chainhook node.
2. Check the highest Bitcoin block retained by Chainhook.