spi: tests: implement half-duplex tests

[erwango]

Is your enhancement proposal related to a problem? Please describe.

#75983 is adding half-duplex support to STM32 devices.
I don't know if this is the first driver in tree supporting this feature, but for sure we miss a test in tree to ensure non regression of the feature.

Describe the solution you'd like
Implement a half-duplex test.
This could be done as a variant of tests/drivers/spi/spi_controller_peripheral or be a separate tests/drivers/spi/half_duplex

[malto101]

Hey @erwango , Is it okay if I pick this up if this isn't already picked up.

[erwango]

Sure, it would be great !
Don't hesitate to rely on #75983 as I don't know if there are others examples of drivers supporting it.

[senerferhat]

Hi @erwango , I noticed that someone had expressed interest in working on this issue, but it seems there hasn't been any visible progress for a while. If it's okay, I’d like to work on implementing the half-duplex SPI test. Please let me know if I can take this up.
I’ll refer to #75983 as suggested for details and ensure the tests align with existing patterns. Let me know if there are any additional requirements or guidance. Thank you!

[erwango]

@senerferhat Sure, go ahead. You can also try to contact @malto101 to get heads up on his progress on this task.