libcli/smb: add struct smb_transports infrastructure

libcli/smb: add struct smb_transports infrastructure

This will be able to use a structure instead of
a string array with int string values for 'smb ports'.

We'll soon add support for smb over quic, so
we need something better than tcp ports with
139 being special.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>