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_sendall.py

@@ -25,10 +25,6 @@ def cleanup(func):
     return wrapper
 
 class SendallTest(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()
 
@@ -303,10 +299,7 @@ class SendallTest(BitcoinTestFramework):
             "desc": utxo["desc"],
             "timestamp": 0,
         }]
-        if self.options.descriptors:
-            watchonly.importdescriptors(import_req)
-        else:
-            watchonly.importmulti(import_req)
+        watchonly.importdescriptors(import_req)
 
         sendall_tx_receipt = watchonly.sendall(recipients=[self.remainder_target], inputs=[utxo])
         psbt = sendall_tx_receipt["psbt"]