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.

src/test/app/MPToken_test.cpp

@@ -1694,15 +1694,6 @@ class MPToken_test : public beast::unit_test::suite
                 jv[jss::SendMax] = mpt.getJson(JsonOptions::none);
                 test(jv, jss::SendMax.c_str());
             }
-            // EscrowCreate
-            {
-                Json::Value jv;
-                jv[jss::TransactionType] = jss::EscrowCreate;
-                jv[jss::Account] = alice.human();
-                jv[jss::Destination] = carol.human();
-                jv[jss::Amount] = mpt.getJson(JsonOptions::none);
-                test(jv, jss::Amount.c_str());
-            }
             // OfferCreate
             {
                 Json::Value jv = offer(alice, USD(100), mpt);