Merge bitcoin/bitcoin#30625: chainparams: Handle Testnet4 in GetNetworkForMagic

b0ec871 chainparams: Handle Testnet4 in GetNetworkForMagic (Fabian Jahr)

Pull request description:

  Found during testing: The recently introduced `GetNetworkForMagic()` doesn't handle Testnet4 yet.

ACKs for top commit:
  tdb3:
    cr ACK b0ec871
  maflcko:
    review ACK b0ec871
  theStack:
    ACK b0ec871
  willcl-ark:
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Tree-SHA512: 77cd0a6791529e5c5dfdb25cff3eff77224be9058d7cf4a8b3544651eb44c5e8ee90c5abfb9751ab0e11c5aa2d8477831dbf1868c4d5909481e0979e4db1eb28

Author: fanquake

src/kernel/chainparams.cpp

@@ -685,13 +685,16 @@ std::optional<ChainType> GetNetworkForMagic(const MessageStartChars& message)
 {
     const auto mainnet_msg = CChainParams::Main()->MessageStart();
     const auto testnet_msg = CChainParams::TestNet()->MessageStart();
+    const auto testnet4_msg = CChainParams::TestNet4()->MessageStart();
     const auto regtest_msg = CChainParams::RegTest({})->MessageStart();
     const auto signet_msg = CChainParams::SigNet({})->MessageStart();
 
     if (std::equal(message.begin(), message.end(), mainnet_msg.data())) {
         return ChainType::MAIN;
     } else if (std::equal(message.begin(), message.end(), testnet_msg.data())) {
         return ChainType::TESTNET;
+    } else if (std::equal(message.begin(), message.end(), testnet4_msg.data())) {
+        return ChainType::TESTNET4;
     } else if (std::equal(message.begin(), message.end(), regtest_msg.data())) {
         return ChainType::REGTEST;
     } else if (std::equal(message.begin(), message.end(), signet_msg.data())) {