rpc: simplify getaddressinfo labels, deprecate previous behavior

- change the value returned in the RPC getaddressinfo `labels` field to an array
  of label name strings

- deprecate the previous behavior of returning a JSON hash structure containing
  label `name` and address `purpose` key/value pairs

- update the relevant tests

test/functional/wallet_listreceivedby.py

@@ -11,10 +11,7 @@ from test_framework.util import (
     assert_equal,
     assert_raises_rpc_error,
 )
-from test_framework.wallet_util import (
-    labels_value,
-    test_address,
-)
+from test_framework.wallet_util import test_address
 
 
 class ReceivedByTest(BitcoinTestFramework):
@@ -131,7 +128,7 @@ class ReceivedByTest(BitcoinTestFramework):
         # set pre-state
         label = ''
         address = self.nodes[1].getnewaddress()
-        test_address(self.nodes[1], address, label=label, labels=labels_value(name=label))
+        test_address(self.nodes[1], address, label=label, labels=[label])
         received_by_label_json = [r for r in self.nodes[1].listreceivedbylabel() if r["label"] == label][0]
         balance_by_label = self.nodes[1].getreceivedbylabel(label)