refactor: add UNKNOWN OutputType

add to enum, array and handle UNKNOWN in various case statements

src/wallet/scriptpubkeyman.cpp

@@ -1966,6 +1966,11 @@ bool DescriptorScriptPubKeyMan::SetupDescriptorGeneration(const CExtKey& master_
         desc_prefix = "tr(" + xpub  + "/86'";
         break;
     }
+    case OutputType::UNKNOWN: {
+        // We should never have a DescriptorScriptPubKeyMan for an UNKNOWN OutputType,
+        // so if we get to this point something is wrong
+        assert(false);
+    }
     } // no default case, so the compiler can warn about missing cases
     assert(!desc_prefix.empty());