Expose `redis_db` via `nslsii.configure_base`

[mrakitin]

It will be an argument to the Redis(...) arg in:

nslsii/nslsii/__init__.py

Line 138 in af27d8a

md = RedisJSONDict(Redis(redis_url), prefix=redis_prefix)

like in this example: https://github.com/redis/redis-py/?tab=readme-ov-file#basic-example