Batch changes: Cache data against a specifc batch change

Created by: umpox

We might be able to cache the result of querying against a batch change to improve performance within this part of the app.

1. Go to batch change, e.g. https://k8s.sgdev.org/organizations/sourcegraph/batch-changes/release-sourcegraph-3.31.0
2. Navigate between tabs as if you were inspecting the change
3. Notice that we always refetch data even if a user has loaded a tab previously

Caching this data might be a good performance boost as it is unlikely to change. What do you think?