test: remove legacy wallet functional tests

Removes all legacy wallet specific functional tests.

Also removes the --descriptor and --legacy-wallet options as these are
no longer necessary with the legacy wallet removed.

test/functional/feature_pruning.py

@@ -66,13 +66,11 @@ def calc_usage(blockdir):
     return sum(os.path.getsize(blockdir + f) for f in os.listdir(blockdir) if os.path.isfile(os.path.join(blockdir, f))) / (1024. * 1024.)
 
 class PruneTest(BitcoinTestFramework):
-    def add_options(self, parser):
-        self.add_wallet_options(parser)
-
     def set_test_params(self):
         self.setup_clean_chain = True
         self.num_nodes = 6
         self.supports_cli = False
+        self.uses_wallet = None
 
         # Create nodes 0 and 1 to mine.
         # Create node 2 to test pruning.