bugfix: disallow label for ranged descriptors & allow external non-ranged descriptors to have label

* do not only check user provided range data to decide whether descriptor is ranged
* properly handle std::optional<bool> when checking if descriptor is internal

test/functional/wallet_rescan_unconfirmed.py

@@ -65,7 +65,8 @@ class WalletRescanUnconfirmed(BitcoinTestFramework):
         assert tx_parent_to_reorg["txid"] in node.getrawmempool()
 
         self.log.info("Import descriptor wallet on another node")
-        descriptors_to_import = [{"desc": w0.getaddressinfo(parent_address)['parent_desc'], "timestamp": 0, "label": "w0 import"}]
+        # descriptor is ranged - label not allowed
+        descriptors_to_import = [{"desc": w0.getaddressinfo(parent_address)['parent_desc'], "timestamp": 0}]
 
         node.createwallet(wallet_name="w1", disable_private_keys=True)
         w1 = node.get_wallet_rpc("w1")