debug: tracing: Add CPU stats module

Change adds CPU stats module for tracing hooks. Module provides
information about percent of CPU usage based on tracing hooks
for threads switching in and out, interrupts enters and exits.
cpu_stats only distinguishes between idle thread, non idle
thread and scheduler.

Signed-off-by: Marek Pieta <Marek.Pieta@nordicsemi.no>
5 files changed