Compute stack_trace inside the tracepoint probe

Using code block for macro parameters allows to run arbitrary code in addition
to return value. The function stack_trace_get_size() computes the actual stack
trace, while stack_trace_get_entries() return previously computed values. We
disable preemption to make sure the code stays on the same CPU for the whole
duration of tracepoint execution. Since sys_entry can't be called from IRQ
context, no nesting can occur.

Signed-off-by: Francis Giraldeau <francis.giraldeau@gmail.com>