test: add option to speed up tx relay/mempool sync

when `self.noban_tx_relay=True`, the following flag
`-whitelist=noban,in,out@127.0.0.1`is added to `extra_args`
to speed up tx relay/mempool sync.

test/functional/mempool_packages.py

@@ -27,10 +27,11 @@ assert CUSTOM_DESCENDANT_LIMIT >= CUSTOM_ANCESTOR_LIMIT
 class MempoolPackagesTest(BitcoinTestFramework):
     def set_test_params(self):
         self.num_nodes = 2
+        # whitelist peers to speed up tx relay / mempool sync
+        self.noban_tx_relay = True
         self.extra_args = [
             [
                 "-maxorphantx=1000",
-                "-whitelist=noban@127.0.0.1",  # immediate tx relay
             ],
             [
                 "-maxorphantx=1000",