[Libraries] [Collections] [Backend] store collections in Studio Library Index

[bradenmacdonald]

As a content author, I want to be able to view and find collections alongside components when searching, browsing, or filtering the contents of a v2 library.

1. Store Collections in the studio Meilisearch content index, in a very similar way to how we store XBlocks (components).
2. Adding them to the index should follow a similar approach to how we index Libraries and Courses.