FE Support batch diff loading

What does this MR do?

Breaks up loading diff data into batches under these conditions:

1. The feature flag diffs_batch_load is enabled.
2. The currently viewed commit is the latest version.

Related issues

#31288 (closed) #31290 (closed)

How to test

• Checkout this MR's branch
• Set diffs_batch_load feature flat locally
  • In terminal rails c
  • Feature.enable(:diffs_batch_load)
• Open dev tools in your browser
• Open up any MR and go to the changes tab
• You should see network calls for diffs_batch.json and diffs_metadata.json

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Code review guidelines
• Merge request performance guidelines
• Style guides