Write to cache entries read but not served to Consumers

[eolivelli]

This is a POC PR to solve apache#16421

the problem that it is trying to solve is that when you are using batching the consumer receives N entries, containing M messages (with M >> N), then it exhaust quickly its permits and at the next dispatcher round the dispatcher loads too many messages from storage (BK or TieredStorage).
there is a bunch of entries that are read but cannot be dispatched, so we are wasting precious reads.
my latest change adds back to the "cache" the entries that have not been dispatched, so that at the second round the entries are still in the cache and we save from reading from tiered storage (or even BK!) again the same data.
This will be a good improvement also for non offloaded shared subscription.
the change applies only to Shared Subscriptions

[eolivelli]

this patch is based on #101