netbios: support a list of names in nbns_resolve

[Skarthik06]

Fixes #5202

nbns_resolve() used the unhashable qname (a list or a bytearray) in its cache key, which raised a TypeError. A list of names is now resolved one name at a time and returned as a dict {name: result}; a bytearray is converted to bytes. Single-name behaviour is unchanged.

Reproduction (before the fix):

from unittest import mock
from scapy.layers.netbios import nbns_resolve
with mock.patch("scapy.layers.netbios.conf.route.get_if_bcast",
                return_value=["192.0.2.255"]):
    nbns_resolve(["ALPHA", "BETA"], iface="test")

This PR was written with the help of AI (Claude Sonnet 5.5).