Add TestNet4 for Bitcoin

[turbolay]

Fixes #1216

This PR doesn't replace TestNet by TestNet4, it simply adds to Network and Bitcoin the field TestNet4. Most interesting file to look at is Network.cs

I also replicated some of the tests we have for TestNet to TestNet4

I used @jlopp 's value for network magic.

I however don't know what to use as vSeeds:

NBitcoin/NBitcoin/Network.cs

Lines 2288 to 2295 in 828b7d9

	#if !NOSOCKET
	vFixedSeeds.Clear();
	vSeeds.Clear();
	vSeeds.Add(new DNSSeedData("bitcoin.jonasschnelli.ch", "testnet-seed.bitcoin.jonasschnelli.ch"));
	vSeeds.Add(new DNSSeedData("tbtc.petertodd.org", "seed.tbtc.petertodd.org"));
	vSeeds.Add(new DNSSeedData("bitcoin.sprovoost.nl", "seed.testnet.bitcoin.sprovoost.nl"));
	vSeeds.Add(new DNSSeedData("bluematt.me", "testnet-seed.bluematt.me"));
	#endif

[mathis1337]

These are the only two I am aware of for the vSeeds right now:

vSeeds.emplace_back("seed.testnet4.bitcoin.sprovoost.nl."); // Sjors Provoost
vSeeds.emplace_back("seed.testnet4.wiz.biz."); // Jason Maurice

You can verify this here: https://github.com/fjahr/bitcoin/blob/2024-04-testnet-4-fix/src/kernel/chainparams.cpp#L350
and the official PR: https://github.com/bitcoin/bitcoin/pull/29775/files#diff-e20339c384d6f19b519ea2de7f4ba4fed92a36d66a80f0339b09927c3fa38d6dR350

[mathis1337]

I added a PR to yours, so you can merge in if you want.
turbolay#1

[turbolay]

Thanks!! Not sure why I missed that.
We will review this PR next week with @lontivero and ping NDorier when we will be sure that it's mergeable

[lontivero]

ACK. It connects to the p2p network and interacts with it flawlessly. What else should I test? @NicolasDorier ?

[NicolasDorier]

Do not add ChainName.Testnet4. This is something specific to Bitcoin, while the ChainName type is not.
You can use a static variable Testnet4ChainName in the Bitcoin type, and handle the case in the GetNetwork.

[turbolay]

This change is why I took so long to push: I'm not sure if it's correct to have this public. I tried another approach and move TestNet4 to Bitcoin class but ended up with a similar (worse probably) problem, see

[turbolay]

@lontivero Can you check at last commit please? 9b4a9aa
I also made this approach for the PR, not sure which is best as they both look bad.

[lontivero]

I don't have context. Why is not okay to have a ChainName for testnet4?

[farukterzioglu]

I don't have context. Why is not okay to have a ChainName for testnet4?

@lontivero testnet4 is only for Bitcoin. Other blockchains (Litecoin, Dash etc.) don't have that.

@turbolay do you have any blocker to have progress with this, is it ready to be reviewed? Relevant change is already merged to Bitcoin Core.

[turbolay]

@farukterzioglu I think it's OK, even if the solution doesn't look like the best

Please also considerate this alternative, that makes other kind of compromises: turbolay@abc2aec#diff-12355e5baf374196ed9c5a0708f16632568b4bfc9139c8daff9aca066fd9f8e1

Feel free to request changes, I would apply fast, or take over the PR.

[farukterzioglu]

@NicolasDorier, above lontivero confirmed it can connect to the new testnet. And it is refactored as you suggested above.
Does the rest look good? Would you have additional comment?

[Kukks]

Can you rebase? We moved things around to get everything cleaner

[turbolay]

Can you rebase? We moved things around to get everything cleaner

Sorry I am busy lately, thank you for the refactor, it looks good indeed. I will rebase tonight.

[Kukks]

Wow, this is a horrible converter with so many hardcoded stuff. It should use Network natively..