Trace

Still requires a few fixes, but the main part is done.
Makes sense.
Having a *hard* limit on number of frames is actually quite nice. But.
Enforce it in kt_func_entry then by counting call depth. Race reporting is too late and very infrequent. So instead of a long-awaited true positive on trinity, we will just get a crash.
But if you do it in kt_func_entry, and over time we will set the right value for KT_MAX_STACK_FRAMES, that will be nice.