Consumer rotate stream

Perform the action of rotating a stream locally or send the command to
do it on the relayd. Rotating a stream file consists of:
 - closing the current tracefile and index,
 - opening a new tracefile and index in the new chunk folder,
 - resetting the stream rotation flags,
 - updating the counter of streams waiting for a rotation in a channel,

If the stream is a metadata stream, we also need to trigger the action
to re-dump the content of the metadata cache after the rotation has been
performed.

The caller of lttng_consumer_rotate_stream() always calls
consumer_post_rotation() after having released the stream lock to update
the counter of streams waiting for a rotation in a channel and notifying
the session daemon if this counter reaches 0.

Signed-off-by: Julien Desfossez <jdesfossez@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>