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/protocol/detail/ledger_entries.macro

@@ -503,3 +503,31 @@ LEDGER_ENTRY(ltORACLE, 0x0080, Oracle, ({
     {sfPreviousTxnID,        soeREQUIRED},
     {sfPreviousTxnLgrSeq,    soeREQUIRED},
 }))
+
+/** A ledger object which tracks MPTokenIssuance
+    \sa keylet::mptIssuance
+ */
+LEDGER_ENTRY(ltMPTOKEN_ISSUANCE, 0x007e, MPTokenIssuance, ({
+    {sfIssuer,                   soeREQUIRED},
+    {sfSequence,                 soeREQUIRED},
+    {sfTransferFee,              soeDEFAULT},
+    {sfOwnerNode,                soeREQUIRED},
+    {sfAssetScale,               soeDEFAULT},
+    {sfMaximumAmount,            soeOPTIONAL},
+    {sfOutstandingAmount,        soeREQUIRED},
+    {sfMPTokenMetadata,          soeOPTIONAL},
+    {sfPreviousTxnID,            soeREQUIRED},
+    {sfPreviousTxnLgrSeq,        soeREQUIRED},
+}))
+
+/** A ledger object which tracks MPToken
+    \sa keylet::mptoken
+ */
+LEDGER_ENTRY(ltMPTOKEN, 0x007f, MPToken, ({
+    {sfAccount,                  soeREQUIRED},
+    {sfMPTokenIssuanceID,        soeREQUIRED},
+    {sfMPTAmount,                soeDEFAULT},
+    {sfOwnerNode,                soeREQUIRED},
+    {sfPreviousTxnID,            soeREQUIRED},
+    {sfPreviousTxnLgrSeq,        soeREQUIRED},
+}))