Replaces the todo!() in get_sched_param with a real implementation
that returns the default scheduler policy (SCHED_OTHER, priority 0).
On Redox, per-thread scheduling parameters are not exposed because
the microkernel does not provide per-thread scheduler policy queries.
The default matches the Linux fallback in pthread_getattr_np() when
no custom policy was set. get_cpu_clkid() is called for the clock_id
field and falls back to 0 if that returns ENOENT (expected on Redox
where per-CPU clock IDs are not yet implemented).
Red Bear OS
vasilito