rpc: Explain active and internal in listdescriptors

The current help text for active and internal in listdescriptors is not
particularly helpful. They require the reader to already know what those
terms mean. This help text is updated to actually explain the
definitions of those words in context of a descriptor wallet.

Author: achow101

src/wallet/rpc/backup.cpp

@@ -1748,13 +1748,13 @@ RPCHelpMan listdescriptors()
                 {RPCResult::Type::OBJ, "", "", {
                     {RPCResult::Type::STR, "desc", "Descriptor string representation"},
                     {RPCResult::Type::NUM, "timestamp", "The creation time of the descriptor"},
-                    {RPCResult::Type::BOOL, "active", "Activeness flag"},
-                    {RPCResult::Type::BOOL, "internal", true, "Whether this is an internal or external descriptor; defined only for active descriptors"},
-                    {RPCResult::Type::ARR_FIXED, "range", true, "Defined only for ranged descriptors", {
+                    {RPCResult::Type::BOOL, "active", "Whether this descriptor is currently used to generate new addresses"},
+                    {RPCResult::Type::BOOL, "internal", /*optional=*/true, "True if this descriptor is used to generate change addresses. False if this descriptor is used to generate receiving addresses; defined only for active descriptors"},
+                    {RPCResult::Type::ARR_FIXED, "range", /*optional=*/true, "Defined only for ranged descriptors", {
                         {RPCResult::Type::NUM, "", "Range start inclusive"},
                         {RPCResult::Type::NUM, "", "Range end inclusive"},
                     }},
-                    {RPCResult::Type::NUM, "next", true, "The next index to generate addresses from; defined only for ranged descriptors"},
+                    {RPCResult::Type::NUM, "next", /*optional=*/true, "The next index to generate addresses from; defined only for ranged descriptors"},
                 }},
             }}
         }},