lib: os: add sys_sem data type

For systems with userspace, the sys_sem exist in user memory working
as counter semaphore for user mode thread. The implemention of sys_sem
is based on k_futex. And the majority of the synchronization operations
are performed in user mode to reduce the calling of system call.
And for systems without userspace enabled, sys_sem behaves like k_sem.

Fixes: #15139.

Signed-off-by: Wentong Wu <wentong.wu@intel.com>