Drop TableView Support

[jessesquires]

CollectionView has advanced sufficiently with UICollectionLayoutListConfiguration, etc. such that TableView simply isn't worth supporting — much less trying to "unify" the APIs between collections and tables.

The List APIs for CollectionView are iOS 14+, but with iOS 15 on the horizon, it's not really worth any of this effort at this point to support iOS 13 or table view. (At least, I certainly won't be deploying to iOS 13.)

If users want good table view support with a similar API, they should use ReactiveLists.

See:

• https://pspdfkit.com/blog/2020/the-case-for-lists-in-uicollectionview/
• https://useyourloaf.com/blog/creating-lists-with-collection-view/

Legacy branch created in case we need/want to reference this:
https://github.com/jessesquires/ReactiveCollectionsKit/tree/legacy-table-view-support