Refactor ImporterFactory for multiple files into a finder

[manasaV3]

Motivation

The MultiSourceFileFinder is a special case of the DefaultImporterFactory which has a different behaviour than other ImporterFactories. It was created to handle when we have multiple files that need to be fetched for a single entity, ie all the files retrieved in a single source entry are will be passed as input for processing the said entity.

This is used for the alignment importer, where we have multiple different files that need to be fetched for a single alignment entity.

This is a low-lift solution and can be a little opaque for the config creator on the behaviour of how the files are processed. This should be refactored to be a finder which supports all the different cases such as source_glob, source_multi_glob, literal, etc. That will make it more intuitive.

Definition of Done

• There is a new finder for this specific usecase
• All the existing configs that utilize this ImporterFactory have been updated to the new finder.
• The existing MultiSourceFileFinder has been sunset