tests/boards/intel_adsp/smoke: Add cpu halt/restart case

Add code to exercise soc_adsp_halt_cpu() and validate the cores can be
restarted with the kernel z_smp_start_cpu() API.

Note that this interface is for 1.8+ devices only.  On cAVS 1.5, the
core power is actually controlled by the host.

Signed-off-by: Andy Ross <andrew.j.ross@intel.com>