testnet4 support

[jlopp]

We're expecting testnet4 to launch in the coming months and be a part of the next Bitcoin Core release. PR is here: bitcoin/bitcoin#29775

[dangershony]

Hi Jamson, thanks for the update.
The Blockcore fullnode has only been upgraded til protocol version 70013, unfortunately we have not implemented support beyond the segwit deployment.

It is my hope that I can at some point implement the next upgrades (mainly compact blocks and taproot), however I am personally busy on another bitcoin related project right now.