feat: add passive Modbus TCP decoding

[ShmalexM]

No description provided.

[josiahlashley21]

Hey, this looks great, especially the request/response pairing.
One thing I was working on it that in OT investigations we also can get exact write values (not just FC + address), e.g. catching a non-HMI write like 1025=10.
So, can we add register_values / coil_values (already under excluded_from_v1) in a follow-up? We’ve already pointed our investigation skill at those names. Write values alone would merge what I am working on and what you are doing here nicely