[Celestica] rma-showtech: get GPIO line value of current direction in rma-showtech GPIO show

[CliffyWong]

Pre-submission checklist

• I've ran the linters locally and fixed lint errors related to the files I modified in this PR. You can install the linters by running pip install -r requirements-dev.txt && pre-commit install
• pre-commit run

Summary

This pull introduces a safe method for reading GPIO line values without altering the pin's current direction.

Motivation

rma-showtech invokes GpiodLine::getValue() to display GPIO pin states. However, getValue() internally calls gpiod_line_request_input(), which forcibly changes the GPIO pin direction to input mode. This behavior can lead to a mismatch with the actual hardware state and may even disrupt ongoing services.
Therefore, introduce a function,GpiodLine::getLineValue(), which reads the GPIO state while respecting its currently direction and integrates it into rma-showtech. This ensures that the rma-showtech GPIO display is non-disruptive.

The modifications include:

• Implemented the new function GpiodLine::getLineValue() to read the value of a GPIO line based on its current direction.
• Updated the Utils::printGpio utility to use the new GpiodLine::getLineValue() function

Test Plan

1. Catch the santa platform snapshot via rma-showtech succesfully.
2. Change several GPIO line to output direction via cmd gpioset, show GPIO information via rma-showtech GPIO show. The value of output direction of these GPIO Lines could be shown correctly.

Before gpioset:

After gpioset:

[meta-codesync]

@mikechoifb has imported this pull request. If you are a Meta employee, you can view this in D106028029.