Rename list cache tag suffixes from 's' to '_list'

Problem/Motivation

From #2304987: Don't invalidate cache tags of referenced entities, use entity list cache tags correctly, add test coverage for entity list cache tags:

Just appending and 's' to the end is still strange, I didn't like that before either. Some entity types this is weird with:

- block_content > block_contents
- editor > editors
- menu_link_content > menu_link_contents
- taxonomy_vocabulary > taxonomy_vocabularys

Proposed resolution

Replace all usages of $entity_type/$whatever . 's' in getListCacheTags() to a '_list' suffix instead.

Remaining tasks

User interface changes

API changes