add --sort-by argument when fetching events

[dciancio]

It would be really nice to add the --sort-by argument to omc get events to support the sorting of events by timestamp, for example, like we do for oc cli.
omc get events --sort-by='metadata.creationTimestamp'

[oarribas]

If #183 can be added, the omc events output should give the output sorted like oc events does.