Add some pthread-related syscalls

[AuYang261]

I added following syscalls:

1. pthread_mutex_destroy
2. pthread_cond_destroy
3. pthread_cond_timedwait
4. pthread-key-related functions, including:

1. pthread_key_create
2. pthread_key_delete
3. pthread_getspecific
4. pthread_setspecific

And I added test code for the above syscalls in apps/c/pthreads/basic.

[coolyjg]

Why this pr contains the same code as #14 ? They should be separated. Or close either of them.

[AuYang261]

They really should be separated. But they should all be come after #18 for passing CI.

#18 should be merged as soon as possible, so that subsequent commits can pass the CI.

[AuYang261]

I rebased the branch to seperate each pr.

[AuYang261]

I searched some meterial and believed that TSD and TLS are different concepts. So the implement of TSD current is not duplicated.

[coolyjg]

TSD is more like a libc conception rather than a kernel conception. Musl libc organizes TSD in pthread_t->tsd. Since we specially treat pthread lib, I think it's okay to follow your design.

[coolyjg]

Please change some code mentioned here, especially error handling (always remember to handle error, and print log), and please remove pthread-key-related functions test into another test file, since pthread/basic only contains tests for frequently used functions.