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/test_framework/test_shell.py

@@ -18,11 +18,8 @@ class TestShell:
     start a single TestShell at a time."""
 
     class __TestShell(BitcoinTestFramework):
-        def add_options(self, parser):
-            self.add_wallet_options(parser)
-
         def set_test_params(self):
-            pass
+            self.uses_wallet = None
 
         def run_test(self):
             pass