PERF: Load topic bookmarks for the user in user_post_bookmarks (PR #10197)

Instead of loading all of the user bookmarks using all the post IDs in a topic, load all the bookmarks for a user using the topic ID. This eliminates a costly WHERE ID IN query.


oh … awesome … bookmark is already denomalized, this makes this easy.

I am mixed on adding more work here, but technically if you somehow got a bookmark on a deleted post or post you can not see, does the system at least recover from this? Will this change cause any issues?

Feel free to merge.