test: add functional test for -discover

test/functional/test_runner.py

@@ -277,6 +277,7 @@ BASE_SCRIPTS = [
     'feature_dersig.py',
     'feature_cltv.py',
     'rpc_uptime.py',
+    'feature_discover.py',
     'wallet_resendwallettransactions.py --legacy-wallet',
     'wallet_resendwallettransactions.py --descriptors',
     'wallet_fallbackfee.py --legacy-wallet',