Improve the overall of perceived performance in the search requests

[brunoocasali]

Description
Based on the discussion of #120

Our internal search handling is:

• make search request to meili asking for all the fields
• mapping only the "primary fields" or just the "id" if there is no extra config.
• make a SELECT in the database to load the AR records.

If we only require the needed fields, we will be able to reduce the memory, CPU overload and time needed to process the requests, improving the search time experience we offer in this gem.

It is also important to note, that we must ensure the other features are still working.