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/TER.cpp

@@ -42,6 +42,9 @@ transResults()
             TERUnderlyingType,
             std::pair<char const* const, char const* const>> const results
     {
+        MAKE_ERROR(tecAMM_BALANCE,                   "AMM has invalid balance."),
+        MAKE_ERROR(tecAMM_INVALID_TOKENS,            "AMM invalid LP tokens."),
+        MAKE_ERROR(tecAMM_FAILED,                    "AMM transaction failed."),
         MAKE_ERROR(tecCLAIM,                         "Fee claimed. Sequence used. No action."),
         MAKE_ERROR(tecDIR_FULL,                      "Can not add entry to full directory."),
         MAKE_ERROR(tecFAILED_PROCESSING,             "Failed to correctly process transaction."),
@@ -58,6 +61,7 @@ transResults()
         MAKE_ERROR(tecOVERSIZE,                      "Object exceeded serialization limits."),
         MAKE_ERROR(tecUNFUNDED,                      "Not enough XAH to satisfy the reserve requirement."),
         MAKE_ERROR(tecUNFUNDED_ADD,                  "DEPRECATED."),
+        MAKE_ERROR(tecUNFUNDED_AMM,                  "Insufficient balance to fund AMM."),
         MAKE_ERROR(tecUNFUNDED_OFFER,                "Insufficient balance to fund created offer."),
         MAKE_ERROR(tecUNFUNDED_PAYMENT,              "Insufficient balance to send."),
         MAKE_ERROR(tecOWNERS,                        "Non-zero owner count."),
@@ -140,6 +144,7 @@ transResults()
         MAKE_ERROR(telIMPORT_VL_KEY_NOT_RECOGNISED, "Import vl key was not recognized."),
         MAKE_ERROR(telCAN_NOT_QUEUE_IMPORT,   "Import transaction was not able to be directly applied and cannot be queued."),
         MAKE_ERROR(temMALFORMED,                 "Malformed transaction."),
+        MAKE_ERROR(temBAD_AMM_TOKENS,            "Malformed: Invalid LPTokens."),
         MAKE_ERROR(temBAD_AMOUNT,                "Can only send positive amounts."),
         MAKE_ERROR(temBAD_CURRENCY,              "Malformed: Bad currency."),
         MAKE_ERROR(temBAD_EXPIRATION,            "Malformed: Bad expiration."),
@@ -192,6 +197,7 @@ transResults()
         MAKE_ERROR(terQUEUED,                 "Held until escalated fee drops."),
         MAKE_ERROR(terPRE_TICKET,             "Ticket is not yet in ledger."),
         MAKE_ERROR(terNO_HOOK,                "No hook with that hash exists on the ledger."),
+        MAKE_ERROR(terNO_AMM,                 "AMM doesn't exist for the asset pair."),
 
         MAKE_ERROR(tesSUCCESS,                "The transaction was applied. Only final in a validated ledger."),
         MAKE_ERROR(tesPARTIAL,                "The transaction was applied but should be submitted again until returning tesSUCCESS."),