z_mutex_init and other functions returns positive error values [Bug]

[milyin]

Describe the bug

int8_t zp_mutex_init(zp_mutex_t *m) { return pthread_mutex_init(m, 0); }
int8_t zp_mutex_free(zp_mutex_t *m) { return pthread_mutex_destroy(m); }

The error values returned by pthread_mutex_init can be positive:
https://pubs.opengroup.org/onlinepubs/7908799/xsh/pthread_mutex_init.html
https://github.com/openbsd/src/blob/8700ed7d87c3b82368687dfae3281b306aecbe66/sys/sys/errno.h

But in zenoh c interface it's assumed that error value should always be negative.

To reproduce

System info

[sashacmc]

@milyin please assign it to me