Introduce AMM support (XLS-30d): (#4294)

Add AMM functionality:
- InstanceCreate
- Deposit
- Withdraw
- Governance
- Auctioning
- payment engine integration

To support this functionality, add:
- New RPC method, `amm_info`, to fetch pool and LPT balances
- AMM Root Account
- trust line for each IOU AMM token
- trust line to track Liquidity Provider Tokens (LPT)
- `ltAMM` object

The `ltAMM` object tracks:
- fee votes
- auction slot bids
- AMM tokens pair
- total outstanding tokens balance
- `AMMID` to AMM `RootAccountID` mapping

Add new classes to facilitate AMM integration into the payment engine.
`BookStep` uses these classes to infer if AMM liquidity can be consumed.

The AMM formula implementation uses the new Number class added in #4192.
IOUAmount and STAmount use Number arithmetic.

Add AMM unit tests for all features.

AMM requires the following amendments:
- featureAMM
- fixUniversalNumber
- featureFlowCross

Notes:
- Current trading fee threshold is 1%
- AMM currency is generated by: 0x03 + 152 bits of sha256{cur1, cur2}
- Current max AMM Offers is 30

---------

Co-authored-by: Howard Hinnant <howard.hinnant@gmail.com>

src/ripple/protocol/impl/TxFormats.cpp

@@ -85,6 +85,64 @@ TxFormats::TxFormats()
         },
         commonFields);
 
+    add(jss::AMMCreate,
+        ttAMM_CREATE,
+        {
+            {sfAmount, soeREQUIRED},
+            {sfAmount2, soeREQUIRED},
+            {sfTradingFee, soeREQUIRED},
+            {sfTicketSequence, soeOPTIONAL},
+        },
+        commonFields);
+
+    add(jss::AMMDeposit,
+        ttAMM_DEPOSIT,
+        {
+            {sfAsset, soeREQUIRED},
+            {sfAsset2, soeREQUIRED},
+            {sfAmount, soeOPTIONAL},
+            {sfAmount2, soeOPTIONAL},
+            {sfEPrice, soeOPTIONAL},
+            {sfLPTokenOut, soeOPTIONAL},
+            {sfTicketSequence, soeOPTIONAL},
+        },
+        commonFields);
+
+    add(jss::AMMWithdraw,
+        ttAMM_WITHDRAW,
+        {
+            {sfAsset, soeREQUIRED},
+            {sfAsset2, soeREQUIRED},
+            {sfAmount, soeOPTIONAL},
+            {sfAmount2, soeOPTIONAL},
+            {sfEPrice, soeOPTIONAL},
+            {sfLPTokenIn, soeOPTIONAL},
+            {sfTicketSequence, soeOPTIONAL},
+        },
+        commonFields);
+
+    add(jss::AMMVote,
+        ttAMM_VOTE,
+        {
+            {sfAsset, soeREQUIRED},
+            {sfAsset2, soeREQUIRED},
+            {sfTradingFee, soeREQUIRED},
+            {sfTicketSequence, soeOPTIONAL},
+        },
+        commonFields);
+
+    add(jss::AMMBid,
+        ttAMM_BID,
+        {
+            {sfAsset, soeREQUIRED},
+            {sfAsset2, soeREQUIRED},
+            {sfBidMin, soeOPTIONAL},
+            {sfBidMax, soeOPTIONAL},
+            {sfAuthAccounts, soeOPTIONAL},
+            {sfTicketSequence, soeOPTIONAL},
+        },
+        commonFields);
+
     add(jss::OfferCancel,
         ttOFFER_CANCEL,
         {