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/wallet_sendmany.py

@@ -9,10 +9,6 @@ from test_framework.util import assert_raises_rpc_error
 
 
 class SendmanyTest(BitcoinTestFramework):
-    # Setup and helpers
-    def add_options(self, parser):
-        self.add_wallet_options(parser)
-
     def skip_test_if_missing_module(self):
         self.skip_if_no_wallet()