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/test/rpc/NoRipple_test.cpp

@@ -20,6 +20,7 @@
 #include <ripple/protocol/Feature.h>
 #include <ripple/protocol/jss.h>
 #include <test/jtx.h>
+#include <test/jtx/TestHelpers.h>
 
 namespace ripple {
 
@@ -127,10 +128,8 @@ public:
             BEAST_EXPECT(resp[jss::result][jss::alternatives].size() == 1);
 
             auto getAccountLines = [&env](Account const& acct) {
-                Json::Value jv;
-                jv[jss::account] = acct.human();
-                auto const r = env.rpc("json", "account_lines", to_string(jv));
-                return r[jss::result][jss::lines];
+                auto const r = jtx::getAccountLines(env, acct);
+                return r[jss::lines];
             };
             {
                 auto const aliceLines = getAccountLines(alice);