Allow multiple schemas for one shot

[ppinchuk]

It might be good to allow users to provide multiple schemas, which would set up multiple parsers for the one shot extraction.

Key considerations:

• Auto generating queries, heuristic keywords, and keywork scores will become tricker. Might be able to get around this by only merging the "features" and "$descriptions" into a "main" schema and using that as the template
• Allowing custom prompts for text collection and text extraction will have to support a per-schema approach. Likely the safest way to do this is to use a dict keyed by the schema filename (no extension?), but it's kind of ugly. Could also disable custom prompts for a multi-schema input but this seems unnecessarily restrictive. Maybe instead the schema input itself is a dict and then keys can match between those? No matter what, this is kind of a bookkeeping nightmare
• The auto generated collection/text extraction prompts as well as the parsers should be on a 1-per-input schema basis, with the data getting concatenated at the very end like we do for wind/solar