[Research] Improve navigation when there are 100s of batch changes

Created by: malomarrec

Problem

Some of our customers create lots of batch changes (data). This is also the case for CEs running demos: there are more than 100 batch changes on demo even though we clean it up from time to time.

This makes it hard to navigate the batch changes interface and find relevant batch changes. We need to explore how to make navigation work if:

• a company has created 100s of batch changes
• and/or a user has created 100s of batch changes

Use cases

Here are things users want to do that are hard right now, that we should study and improve:

• what batch change needs attention right now?
• what batch changes are active or inactive right now? Relates to https://github.com/sourcegraph/sourcegraph/issues/20738
• which batch changes are done?
• someone had a batch change called my-batch-change, how do I find it among the 100s of batch changes

If we revamp the /batch-changes page, we could take this opportunity to also highlight high level stats about batch changes usage on the instance, and clearly communicate about the ROI of batch changes. Dudley would be interested in collaborating on this, and it'd be helpful for this customer.