support mutability for MPTPrivacy (#6137)

Update lsfMPTNoConfidentialTransfer to lsfMPTPrivacy
Add flag lsmfMPTPrivacy to control the mutability of lsfMPTPrivacy.
disallow mutating lsfMPTPrivacy when lsfMPTPrivacy is not set.
disallow mutating lsfMPTPrivacy when there's confidential outstanding amount.

src/test/app/MPToken_test.cpp

@@ -2931,6 +2931,7 @@ class MPToken_test : public beast::unit_test::suite
                 tmfMPTSetCanTrade | tmfMPTClearCanTrade,
                 tmfMPTSetCanTransfer | tmfMPTClearCanTransfer,
                 tmfMPTSetCanClawback | tmfMPTClearCanClawback,
+                tmfMPTSetPrivacy | tmfMPTClearPrivacy,
                 tmfMPTSetCanLock | tmfMPTClearCanLock | tmfMPTClearCanTrade,
                 tmfMPTSetCanTransfer | tmfMPTClearCanTransfer |
                     tmfMPTSetCanEscrow | tmfMPTClearCanClawback};