Introduce MPT support (XLS-33d): (#5143)

Amendment:
- MPTokensV1

New Transactions:
- MPTokenIssuanceCreate
- MPTokenIssuanceDestroy
- MPTokenIssuanceSet
- MPTokenAuthorize

Modified Transactions:
- Payment
- Clawback

New Objects:
- MPTokenIssuance
- MPToken

API updates:
- ledger_entry
- account_objects
- ledger_data

Other:
- Add += and -= operators to ValueProxy

Read full spec: https://github.com/XRPLF/XRPL-Standards/tree/master/XLS-0033d-multi-purpose-tokens

---------
Co-authored-by: Shawn Xie <shawnxie920@gmail.com>
Co-authored-by: Howard Hinnant <howard.hinnant@gmail.com>
Co-authored-by: Ed Hennis <ed@ripple.com>
Co-authored-by: John Freeman <jfreeman08@gmail.com>

src/test/app/SetAuth_test.cpp

@@ -38,8 +38,8 @@ struct SetAuth_test : public beast::unit_test::suite
         using namespace jtx;
         Json::Value jv;
         jv[jss::Account] = account.human();
-        jv[jss::LimitAmount] =
-            STAmount({to_currency(currency), dest}).getJson(JsonOptions::none);
+        jv[jss::LimitAmount] = STAmount(Issue{to_currency(currency), dest})
+                                   .getJson(JsonOptions::none);
         jv[jss::TransactionType] = jss::TrustSet;
         jv[jss::Flags] = tfSetfAuth;
         return jv;