Priority-inheritance futex is not used when implementing Mutex and RwLock

[ruihe774]

Maybe a duplication of #128231?

AFAIK Mutex and RwLock try to support priority inheritance (and that is why it uses pthread mutex in macOS). I'm curious why they just use normal futexes (FUTEX_WAIT_BITSET and FUTEX_WAKE in sys/pal/unix/futex.rs) and do not utilize priority-inheritance futexes on platforms that support PI futexes, namely FUTEX_LOCK_PI in Linux and UMUTEX_PRIO_INHERIT in FreeBSD. IMO PI futexes have better cooperation with the system scheduler.