test: introduce the default port function and remove hard coded port

tests/utils.py

@@ -8,6 +8,16 @@ import time
 EXPERIMENTAL_FEATURES = env("EXPERIMENTAL_FEATURES", "0") == "1"
 COMPAT = env("COMPAT", "1") == "1"
 
+def default_ln_port(network: str) -> int:
+    network_map = {
+        "bitcoin": 9735,
+        "testnet": 19735,
+        "regtest": 19846,
+        "signet": 39735,
+        "liquid-regtest": 20735,
+        "liquid": 9735, 
+    }
+    return network_map[network]
 
 def anchor_expected():
     return EXPERIMENTAL_FEATURES or EXPERIMENTAL_DUAL_FUND