Allow changing network upgrade parameters on regtest

Derived from upstream commit 56c87e92110f05d7452f1e85bf755246ffc77206:
    Allow changing BIP9 parameters on regtest

src/chainparams.cpp

@@ -402,6 +402,12 @@ public:
         vFoundersRewardAddress = { "t2FwcEhFdNXuFMv1tcYwaBJtYVtMj8b1uTg" };
         assert(vFoundersRewardAddress.size() <= consensus.GetLastFoundersRewardBlockHeight());
     }
+
+    void UpdateNetworkUpgradeParameters(Consensus::UpgradeIndex idx, int nActivationHeight)
+    {
+        assert(idx > Consensus::BASE_SPROUT && idx < Consensus::MAX_NETWORK_UPGRADES);
+        consensus.vUpgrades[idx].nActivationHeight = nActivationHeight;
+    }
 };
 static CRegTestParams regTestParams;
 
@@ -475,3 +481,8 @@ std::string CChainParams::GetFoundersRewardAddressAtIndex(int i) const {
     assert(i >= 0 && i < vFoundersRewardAddress.size());
     return vFoundersRewardAddress[i];
 }
+
+void UpdateNetworkUpgradeParameters(Consensus::UpgradeIndex idx, int nActivationHeight)
+{
+    regTestParams.UpdateNetworkUpgradeParameters(idx, nActivationHeight);
+}