Test network upgrade logic

Also demonstrates how to specify a network upgrade.

src/consensus/params.h

@@ -21,6 +21,7 @@ namespace Consensus {
 enum UpgradeIndex {
     // Sprout must be first
     BASE_SPROUT,
+    UPGRADE_TESTDUMMY,
     // NOTE: Also add new upgrades to NetworkUpgradeInfo in upgrades.cpp
     MAX_NETWORK_UPGRADES
 };

src/consensus/upgrades.cpp

@@ -13,6 +13,11 @@ const struct NUInfo NetworkUpgradeInfo[Consensus::MAX_NETWORK_UPGRADES] = {
         /*.nBranchId =*/ 0,
         /*.strName =*/ "Sprout",
         /*.strInfo =*/ "The Zcash network at launch",
+    },
+    {
+        /*.nBranchId =*/ 0x74736554,
+        /*.strName =*/ "Test dummy",
+        /*.strInfo =*/ "Test dummy info",
     }
 };