Lack of DB usage, duplications and redundancy in scarches api

[farhadmd7]

This snippet is from scVI.py -> pretrained_model is ignored here and load_query_data get called again.
Inefficient snippets like that together with hard coded stuff can be found in other scripts as well

[farhadmd7]

Following snippet is from utils.py: Overall lots of these infos for configurations and other purposes can be fetched either from databases in JSON files or recieved from Backend only if needed.