checks: check for OSD suicide timeouts

OSD can hit suicide timeouts for different reasons, it would be great if ceph-medic could highlight such events from the OSD log files.

Start by examining the OSD log files and how ceph-medic currently performs checks against them. Define which suicide-timeout events must be detected and how they should be highlighted; done means the check reliably reports those events, with tests or sample logs covering the detection.

Written by the indexing model from the issue text.