Support clocks for sync objects

A race still may happen after a few test set runs (in case the same slab object will be used), since completion variables are not handled yet.
don't call this slab, this is not slab, slab is a continuos region of memory holding a set of objects in so-called slab memory allocators
please rename kt_slab_alloc/kt_slab_free/slab to something else
appropriate terms for this entity are 'memory block' or 'memory chunk'