[Spike] Refine diff limits for Rapid Diffs

We need to refine our existing diff limits when using Rapid Diffs. Rapid Diffs impose different limitations on how many diffs and diff lines we can actually render. That might differ with what we have right now. In order to understand these limits we need to test both client-side and server-side performance when rendering substantial amounts of diffs.

If we decided that we need to increase these limits we should introduce separate diff limits just for Rapid Diffs. If these need to be reduced we can already provide them with max_files and max_lines.