Log retention across different versions

[mikolajpe]

Hi, great to see that log retention has been fixed for v7 (#8815) but I would suggest to apply this fix to v5 and v6 as well. Log retention policy existed in v1 and v2 and was done by logrotate. Person who replaced logrotate with log4j in v5 have missed log retention policy and it was missing from that point on, until the fix mentioned before. Lack of retention policy is causing disk overflow and basically makes logstash stop to log whats currently happening.

I think that it would add a lot more clarity if firstly retention policy was available in all versions (at least all that havent reached end of their lifetime) and secondly documentation should state the amount of disk space required for the logstash to operate.