move and rename hash function

this function, xor_hash, and a variable for the default key (as bytes, I think, rather than the base64 version) really all belong in meshtastic.util rather than here.
There's multiple forms of hashing in firmware so this should be named to denote that, perhaps channel_hash. If we later want to add the frequency-slot-style hash, better if it's distinguished better from the start.

meshtastic/node.py

@@ -16,25 +16,19 @@ from meshtastic.util import (
     pskToString,
     stripnl,
     message_to_json,
+    channel_hash,
 )
 
 logger = logging.getLogger(__name__)
 
-def xor_hash(data: bytes) -> int:
-    """Compute an XOR hash from bytes."""
-    result = 0
-    for char in data:
-        result ^= char
-    return result
-
 def generate_hash(name: str, key: str) -> int:
     """generate the channel number by hashing the channel name and psk"""
     if key == "AQ==":
         key = "1PG7OiApB1nwvP+rz05pAQ=="
     replaced_key = key.replace("-", "+").replace("_", "/")
     key_bytes = base64.b64decode(replaced_key.encode("utf-8"))
-    h_name = xor_hash(bytes(name, "utf-8"))
-    h_key = xor_hash(key_bytes)
+    h_name = channel_hash(bytes(name, "utf-8"))
+    h_key = channel_hash(key_bytes)
     result: int = h_name ^ h_key
     return result