Investigate possibility of triggering pro-active data region memory cleanup about aldica

[AFaust]

In some parts of our documentation we may also want to link to some key documentation pages of Ignite to explain the behaviour of our module, e.g. in this case to the memory defragmentation page. In there, we have the explicit statement:

If you delete data from Ignite caches/tables, the cache size and memory use will not decrease because the memory is assigned to Ignite by the OS (and is reserved for later reuse). As for disk/physical memory, typically the Write Ahead Log (WAL) and the contents of Ignite database files on disk only grow in size. That disk space is only freed when caches are deleted. Therefore, if you want to release memory to the OS or delete data to save disk space, you should delete the cache.

So with regards to this issue, we will very likely not be able to trigger a cleanup, but should check if we can provide metrics as to the "actual" used memory that are more precise in the long run - otherwise we may want to just remove that admin console page as it would not provide sufficient value for administrators to warrant the possible confusion.