"find_commit" Gitaly N+1 when fetching commit information on MR

We're currently having N+1 calls for Gitaly find_commit endpoint when presenting discussions:

Steps to reproduce

1. Create a MR
2. Comment on a diff file
3. Outdate this diff file (change it and push)
4. You'll be able to see a new find_commit call for each new outdated file

Seems like we could be batching these requests using Gitlab::Git::Commit.batch_by_oid with BatchLoader, similarly as we lazy load Blobs.