batches: cache bulk operations query, refactor connection

Created by: courier-new

Part 2 of #24417 (closed) and the data fetching migration to Apollo cache for batch change detail queries. Swapping out this query for useConnection involved also migrating from the bulky FilteredConnection to the new connection composition API.

This was basically my "warm-up" for swapping out the connection query for changesets (coming soon...), because this connection's UI block is more standalone.

Again, I didn't get to record a video yet, but now when you swap between tabs on the batch change details page, the bulk operations won't disappear and need to be freshly refetched every time you switch off of that tab! Woohoo!

Based on #25378 since it relies on changes made there.