tests: drivers: Update nrf2 clock control tests for nrf2_auxpll driver

Test added for new nrf2_auxpll driver. Frequency checks are
against known usecases of the auxpll (USB, CAN and AUDIO).
Also update test to be more modular, only running certain tests
if in the devicetree.

Signed-off-by: David Jewsbury <david.jewsbury@nordicsemi.no>