Use whitespace setting on Rapid Diffs page reload

Olaoluwa Olurorequested to merge
509228-rapid-diffs-doesn-t-respect-whitespace-setting-on-page-reload into master

What does this MR do and why?

Problem

This is happening because we're not passing the diff_options to #first_diffs_slice and we're also not considering user preferences in it as well.

Solution

We should also consider the whitespace preference and pass diff_options to MergeRequest#first_diffs_slice.

References

Screenshots or screen recordings

Screen_Recording_2025-03-31_at_14.54.01

How to set up and validate locally

Can follow the steps outlined in the issue's how to reproduce

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #509228 (closed)

Merge request reports