sched_getparam, sched_getscheduler and sched_setparam with the own pid
from a thread other than the main thread act on the main thread once it
has registered through scePthreadSelf, as FreeBSD's p1003_1b.c selects
the first thread. Before registration, after the main thread exits and
on macOS they still throw.
Priorities outside the supported band and the calling process's own pid are unverified and are no longer pinned to throw. The worker test now sets a priority different from the caller's and checks both, so a no-op or a shared value fails.
sched_getparam, sched_getscheduler and sched_setparam are defined under libkernel/Pthread/Posix, so their typed declarations replace the no-argument placeholders in the libkernel header (public_headers requires the declaration in the implementing library's header), and GuestSchedParams.cpp includes the canonical headers instead of declaring these exports and the pthread, getpid and error calls locally.
infra-rig