Add support for XLS-85 Token Escrow (#5185)

- Specification: https://github.com/XRPLF/XRPL-Standards/pull/272
- Amendment: `TokenEscrow`
- Enables escrowing of IOU and MPT tokens in addition to native XRP.
- Allows accounts to lock issued tokens (IOU/MPT) in escrow objects, with support for freeze, authorization, and transfer rates.
- Adds new ledger fields (`sfLockedAmount`, `sfIssuerNode`, etc.) to track locked balances for IOU and MPT escrows.
- Updates EscrowCreate, EscrowFinish, and EscrowCancel transaction logic to support IOU and MPT assets, including proper handling of trustlines and MPT authorization, transfer rates, and locked balances.
- Enforces invariant checks for escrowed IOU/MPT amounts.
- Extends GatewayBalances RPC to report locked (escrowed) balances.

include/xrpl/protocol/jss.h

@@ -391,6 +391,7 @@ JSS(load_fee);                // out: LoadFeeTrackImp, NetworkOPs
 JSS(local);                   // out: resource/Logic.h
 JSS(local_txs);               // out: GetCounts
 JSS(local_static_keys);       // out: ValidatorList
+JSS(locked);                  // out: GatewayBalances
 JSS(low);                     // out: BookChanges
 JSS(lowest_sequence);         // out: AccountInfo
 JSS(lowest_ticket);           // out: AccountInfo