Rollup merge of #148694 - joboet:teeos-sync, r=ChrisDenton

std: support `RwLock` and thread parking on TEEOS

Since TEEOS supports pthread mutexes and condvars, it can share the pthread-based thread parking implementation and thus also the queue-based `RwLock` implementation used on other platforms.

CC ``@petrochenkov`` ``@Sword-Destiny``

Author: Zalathar