String values from Modbus registers return incorrect data due to missing byte/word swap support

# Description:

While working with EdgeX Foundry 4.0 and the device-modbus-go service, I encountered an issue when reading string data from a PLC over Modbus.

The PLC sends string data stored in holding/input registers, but the bytes within each register are swapped (which is common in many PLC implementations).

I attempted to use the isByteSwap and isWordSwap configuration options, but they do not work for string data types in the current version. As a result, the strings received in EdgeX are incorrect or unreadable, since the byte order is reversed compared to the actual PLC data.

# Bug Report

Steps to Reproduce:

1) Configure a Modbus device in EdgeX 4.0 that sends string data through holding registers.
2) Define the resource with valueType: "String", and set isByteSwap and isWordSwap to true.
3) Observe the values received by the device service.

Expected:
The string data should match the value sent from the PLC.

Actual:
The received string data is scrambled or contains swapped characters due to byte order mismatch.

# Environment:-

EdgeX Version: 4.0
Service: device-modbus-go
Protocol: Modbus TCP
Device Type: PLC sending string data in holding registers

Start in device-modbus-go by tracing handling for valueType String and the isByteSwap/isWordSwap options when reading holding/input registers over Modbus TCP. Reproduce the PLC byte-order case described in the issue, then verify that the received string matches the expected PLC value.

Written by the indexing model from the issue text.