Rename trace_event_iter_init() to trace_event_iter_init_pattern(),
add trace_event_iter_init_all() for interating over all events.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20210601132414.432430-3-kraxel@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>