kernel: gather basic thread runtime statistics

This adds the bits to gather the first thread runtime statictic:
thread execution time. It provides a rough idea of how much time
a thread is spent in active execution. Currently it is not being
used, pending following commits where it combines with the trace
points on context switch as they instrument the same locations.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>
5 files changed