Retention policy based on topic size

[spetz]

Currently, the automatic cleanup of expired segments is based only on the time, e.g. delete segments older than 7 days etc.

It could be also beneficial to extend the existing policy with size based approach, for example, the segment is expired thus marked for deletion if the total size of the topic reaches the specific threshold.

It should be possible to enable both policies at the same time (time and size based).

[hubcio]

I will do it.