Augments the Batch functionality to conform to the changes in the specification proposed in PR XRPLF/XRPL-Standards#563 (and slated to be implemented in xrpld via XRPLF/rippled#6446).

Marking this as draft until a valid xrpld container is published. Until then, the ITs in this build won't pass.

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Batch V1.1 Implementation (XLS-0056)

Implements the V1.1 spec changes for the Batch transaction type (XLS-0056).

Key changes

BatchSigners auto-sort (V1.1 wire format requirement)

• Batch.checkBatchSigners() now auto-sorts BatchSigners entries ascending by account address before building, using the same normalizing @Value.Check pattern as BatchSigner#checkAndNormalize(). The on-chain format rejects out-of-order entries with temBAD_SIGNER.
• A sortedBatchSigners guard field prevents infinite recursion during the re-build.

BatchSigners cap and extra-signers rule (V1.1 spec changes)

• Hard cap raised to 8 BatchSigners entries (was: ≤ number of inner transactions).
• "Extra signers" are now allowed: an account may appear in BatchSigners without having its own inner transaction (e.g., co-signers, delegates). xrpl4j no longer rejects these, since whether an extra signer is legitimate requires ledger state.

Signing path (SignatureUtils, AbstractSignatureService, TransactionSigner)

• Updated signing helpers to handle multi-account Batch transactions and the toSignableInnerBytes path required by V1.1.

Docs and validation clarifications

• Expanded Batch.rawTransactions() Javadoc to enumerate every per-inner-transaction rule with enforcement attribution (xrpl4j vs. server-side).
• Corrected a stale comment claiming tfInnerBatchTxn was not enforced at construction time — it has always been enforced by RawTransactionWrapper.check().

Integration tests

• BatchTransactionIT extended to cover V1.1 multi-account batch flows against Testnet/Devnet.