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

[piotrnar]

I will be happy to switch to the new testnet, once it is live - it will not be a technical challenge.

In the meantime, I wish you had not fucked up the old one.
It was not nice, mate.

[jlopp]

It was unfortunate that folks felt like they could violate the fundamental principle of testnet without any repercussions.

Hopefully a little temporary pain will create enough of a lasting impression to prevent future attempts!