Chainparams: Refactor: Decouple main::GetBlockValue() from Params() [renamed GetBlockSubsidy]

Remove redundant getter CChainParams::SubsidyHalvingInterval()

src/chainparams.h

@@ -49,7 +49,6 @@ public:
     const CMessageHeader::MessageStartChars& MessageStart() const { return pchMessageStart; }
     const std::vector<unsigned char>& AlertKey() const { return vAlertPubKey; }
     int GetDefaultPort() const { return nDefaultPort; }
-    int SubsidyHalvingInterval() const { return consensus.nSubsidyHalvingInterval; }
 
     /** Used if GenerateBitcoins is called with a negative number of threads */
     int DefaultMinerThreads() const { return nMinerThreads; }