spi: tests: implement half-duplex tests

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

https://github.com/zephyrproject-rtos/zephyr/pull/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