Trace Chunks: Implement separate store configurability in helmcharts and omnibus

Add the capability to distinctly configure a Redis instance to be used for chunk storage.

1. Charts: At least the _rails.redis.tpl but possibly elsewhere as well) to enable configuration in kubernetes.
2. Omnibus: At least the list of possible redis instances and other places as well.

This needs to make sure the configuration file config/redis.trace_chunks.yml is present in the Rails root of the node/pod

Directly related to #1058 (closed), but can be done independently/in parallel