scripted-diff: Use DataStream in most places

The remaining places are handled easier outside a scripted-diff.

-BEGIN VERIFY SCRIPT-
 sed --regexp-extended -i 's/CDataStream ([0-9a-zA-Z_]+)\(SER_[A-Z]+, [A-Z_]+_VERSION\);/DataStream \1{};/g' $( git grep -l CDataStream)
 sed -i 's/, CDataStream/, DataStream/g' src/wallet/walletdb.cpp
-END VERIFY SCRIPT-

src/external_signer.cpp

@@ -74,7 +74,7 @@ UniValue ExternalSigner::GetDescriptors(const int account)
 bool ExternalSigner::SignTransaction(PartiallySignedTransaction& psbtx, std::string& error)
 {
     // Serialize the PSBT
-    CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
+    DataStream ssTx{};
     ssTx << psbtx;
     // parse ExternalSigner master fingerprint
     std::vector<unsigned char> parsed_m_fingerprint = ParseHex(m_fingerprint);