Port `Thread::timedWait` from Miosix Testing

Supersedes !14 (closed). The lastest implementation of thread timed waits from Miosix Testing was used.

https://github.com/fedetft/miosix-kernel/commit/b33426395e7930837aca2a231f5c24095977ac06

Implementation differences:

• Thread flags weren't modified as opposed to the above commit: the WAIT_COND flag wasn't removed
• The IRQ/getCurrentThread functions weren't modified