Support snapshot max-size limitation

This features allows the user to specify a maximum size for the snapshot
collected. The maximum stream size is split equally by the total number
of streams active at the time of the snapshot record across all the
domains. The metadata is not limited and its size is not taken into
account in the maximum stream size computation.

Signed-off-by: Julien Desfossez <jdesfossez@efficios.com>
Signed-off-by: David Goulet <dgoulet@efficios.com>