Removing 'osv trace summary' and 'osv trace duration' commands from
loader.py. The first is added as 'trace.py summary --timed', the
second one is added as 'trace.py list-timed'.

It was easier to move both in one commit as they are coupled with each
other.

Signed-off-by: Tomasz Grabiec <tgrabiec@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>