hook_page_(attachments|attachments_alter|top|bottom)() should specify the right cacheability metadata

Quoting Wim Leers in #2475749-2: Allow to set #cache metadata in hook_page_attachments() → :

In a follow-up, we should make all hook_page_attachments(), hook_page_attachments_alter(), hook_page_top() and hook_page_bottom() implementations set the right cacheability metadata.

For example, quickedit_page_attachments() only adds its asset library if the current user has the right permission (vary by the 'user.permissions' cache context) and it's not an admin route (no cache context for that yet).