Add a --descriptors option to various tests

Adds a --descriptors option globally to the test framework. This will
make the test create and use descriptor wallets. However some tests may
not work with this.

Some tests are modified to work with --descriptors and run with that
option in test_runer:
* wallet_basic.py
* wallet_encryption.py
* wallet_keypool.py
* wallet_keypool_topup.py
* wallet_labels.py
* wallet_avoidreuse.py

test/functional/test_framework/test_node.py

@@ -62,7 +62,7 @@ class TestNode():
     To make things easier for the test writer, any unrecognised messages will
     be dispatched to the RPC connection."""
 
-    def __init__(self, i, datadir, *, chain, rpchost, timewait, bitcoind, bitcoin_cli, coverage_dir, cwd, extra_conf=None, extra_args=None, use_cli=False, start_perf=False, use_valgrind=False, version=None):
+    def __init__(self, i, datadir, *, chain, rpchost, timewait, bitcoind, bitcoin_cli, coverage_dir, cwd, extra_conf=None, extra_args=None, use_cli=False, start_perf=False, use_valgrind=False, version=None, descriptors=False):
         """
         Kwargs:
             start_perf (bool): If True, begin profiling the node with `perf` as soon as
@@ -80,6 +80,7 @@ class TestNode():
         self.binary = bitcoind
         self.coverage_dir = coverage_dir
         self.cwd = cwd
+        self.descriptors = descriptors
         if extra_conf is not None:
             append_config(datadir, extra_conf)
         # Most callers will just need to add extra args to the standard list below.
@@ -171,10 +172,10 @@ class TestNode():
     def __getattr__(self, name):
         """Dispatches any unrecognised messages to the RPC connection or a CLI instance."""
         if self.use_cli:
-            return getattr(RPCOverloadWrapper(self.cli, True), name)
+            return getattr(RPCOverloadWrapper(self.cli, True, self.descriptors), name)
         else:
             assert self.rpc_connected and self.rpc is not None, self._node_msg("Error: no RPC connection")
-            return getattr(RPCOverloadWrapper(self.rpc), name)
+            return getattr(RPCOverloadWrapper(self.rpc, descriptors=self.descriptors), name)
 
     def start(self, extra_args=None, *, cwd=None, stdout=None, stderr=None, **kwargs):
         """Start the node."""
@@ -266,11 +267,11 @@ class TestNode():
 
     def get_wallet_rpc(self, wallet_name):
         if self.use_cli:
-            return RPCOverloadWrapper(self.cli("-rpcwallet={}".format(wallet_name)), True)
+            return RPCOverloadWrapper(self.cli("-rpcwallet={}".format(wallet_name)), True, self.descriptors)
         else:
             assert self.rpc_connected and self.rpc, self._node_msg("RPC not connected")
             wallet_path = "wallet/{}".format(urllib.parse.quote(wallet_name))
-            return RPCOverloadWrapper(self.rpc / wallet_path)
+            return RPCOverloadWrapper(self.rpc / wallet_path, descriptors=self.descriptors)
 
     def stop_node(self, expected_stderr='', wait=0):
         """Stop the node."""
@@ -598,13 +599,28 @@ class TestNodeCLI():
             return cli_stdout.rstrip("\n")
 
 class RPCOverloadWrapper():
-    def __init__(self, rpc, cli=False):
+    def __init__(self, rpc, cli=False, descriptors=False):
         self.rpc = rpc
         self.is_cli = cli
+        self.descriptors = descriptors
 
     def __getattr__(self, name):
         return getattr(self.rpc, name)
 
+    def createwallet(self, wallet_name, disable_private_keys=None, blank=None, passphrase=None, avoid_reuse=None, descriptors=None):
+        if self.is_cli:
+            if disable_private_keys is None:
+                disable_private_keys = 'null'
+            if blank is None:
+                blank = 'null'
+            if passphrase is None:
+                passphrase = ''
+            if avoid_reuse is None:
+                avoid_reuse = 'null'
+        if descriptors is None:
+            descriptors = self.descriptors
+        return self.__getattr__('createwallet')(wallet_name, disable_private_keys, blank, passphrase, avoid_reuse, descriptors)
+
     def importprivkey(self, privkey, label=None, rescan=None):
         wallet_info = self.getwalletinfo()
         if self.is_cli: