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/LedgerFormats.h

@@ -145,7 +145,8 @@ enum LedgerSpecificFlags {
         0x10000000,               // True, reject new paychans
     lsfDisallowIncomingTrustline =
         0x20000000,               // True, reject new trustlines (only if no issued assets)
-    // 0x40000000 is available
+    lsfAllowTrustLineLocking =
+        0x40000000,               // True, enable trustline locking
     lsfAllowTrustLineClawback =
         0x80000000,               // True, enable clawback