Add Batch feature (XLS-56) (#5060)

- Specification: [XRPLF/XRPL-Standards 56](https://github.com/XRPLF/XRPL-Standards/blob/master/XLS-0056d-batch/README.md)
- Amendment: `Batch`
- Implements execution of multiple transactions within a single batch transaction with four execution modes: `tfAllOrNothing`, `tfOnlyOne`, `tfUntilFailure`, and `tfIndependent`.
- Enables atomic multi-party transactions where multiple accounts can participate in a single batch, with up to 8 inner transactions and 8 batch signers per batch transaction.
- Inner transactions use `tfInnerBatchTxn` flag with zero fees, no signature, and empty signing public key.
- Inner transactions are applied after the outer batch succeeds via the `applyBatchTransactions` function in apply.cpp.
- Network layer prevents relay of transactions with `tfInnerBatchTxn` flag - each peer applies inner transactions locally from the batch.
- Batch transactions are excluded from AccountDelegate permissions but inner transactions retain full delegation support.
- Metadata includes `ParentBatchID` linking inner transactions to their containing batch for traceability and auditing.
- Extended STTx with batch-specific signature verification methods and added protocol structures (`sfRawTransactions`, `sfBatchSigners`).

src/test/jtx/impl/txflags.cpp

@@ -28,7 +28,7 @@ namespace jtx {
 void
 txflags::operator()(Env&, JTx& jt) const
 {
-    jt[jss::Flags] = v_ /*| tfUniversal*/;
+    jt[jss::Flags] = v_ /*| tfFullyCanonicalSig*/;
 }
 
 }  // namespace jtx