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>

include/xrpl/basics/XRPAmount.h

@@ -207,6 +207,10 @@ public:
         return dropsAs<Dest>().value_or(defaultValue.drops());
     }
 
+    /* Clips a 64-bit value to a 32-bit JSON number. It is only used
+     * in contexts that don't expect the value to ever approach
+     * the 32-bit limits (i.e. fees and reserves).
+     */
     Json::Value
     jsonClipped() const
     {