Uncategorized fandoms not listed on collection fandoms page

Steps to reproduce

1. Log in

2. Browse > Collections > New Collection

3. Fill in required information (Collection name, Display title)

4. Press "Submit" to create the collection

5. Follow the "Post to Collection" link

6. Fill in required information, making sure to enter a fandom tag that is either brand new or that appears on the Uncategorized Fandoms page

7. Press "Post"

8. Follow the link to your collection (located in the work's meta)

What happens

1. In the collection's sidebar, the count beside Fandoms is 0

2. When you follow the "Fandoms (0)" link, you see 0 fandoms

3. In the select menu for media types, you see no "Uncategorized Fandoms" option

4. If you go to Collections > Browse, the blurb for the collection says Fandoms: 0

What should happen

1. The count in the sidebar should include any canonical or noncanonical uncategorized fandoms on works in the collection

2. The collection's fandoms page should include those fandoms

3. The select menu should have an "Uncategorized Fandoms" option (and using it should take you to a page listing those fandoms)

4. The count in the blurb for the collection should include any canonical or noncanonical uncategorized fandoms on works in the collection

Notes
Because noncanonical fandoms don't have /works pages, the names of the fandoms will link to the tag page, e.g. https://test.archiveofourown.org/collections/5613_pm/tags/Killing%20Eve. We'll need to make sure the page only includes works in the collection (as opposed to all works with the tag) and also pay attention to caching (we don't want /tags/NAME to show only works in a specific question or /collections/NAME/tags/NAME to show all works due to caching).

Additionally, this will affect – because it applies to counts and you'll need to be able to filter for fandoms containing works in uncategorized fandoms – and should be done first to avoid the need to reindex. Fields this will affect are general_fandom_ids, public_fandom_ids, general_fandoms_count, and public_fandoms_count.