Clustering: Maintain a script to generate default akka configuration for multinode CSIT tests.

Currently there is a script in Integration/Distribution, but it applies assumptions on what the packaged akka.conf looks like, without verifying them.

Ideally, Controller project would host a template and a script. The packaged akka.conf would be generated for 1 node setup, and CSIT will use the same script and template, just generating for different number of nodes (3).

The Integration/Distribution script also generates modules.conf and module-shards.conf, so those files should be covered by this item as well.