feat: allow splitting scrolls into multiple instances

[matiwinnetou]

In order to run scrolls in production, it is necessary to be able to run multiple sled instances on the same sled database.

Dependencies:

1. Allow to configure redis _cursor name via config

2. Separate sled write away from the scrolls. We should have a command line tool that keeps scrolls ingestion process separate from scrolls instance. Scrolls instance should use sled db and only in case reducers are configured that need it