Add diff_id to diff file links

What does this MR do and why?

This MR:

1. Adds diff_id to diff file:
   1. Line links
   2. Header link
2. Refactors the mapParallel code so the dependencies are clear
3. Fixes a bug when no scrolling occurred on file header click (handleFileNameClick callback was given a wrong element selector)
4. Refactors lineHref and related code to use URL class to generate file links. This ensures all the query params are preserved for file links.

MR acceptance checklist

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

How to set up and validate locally

1. Open any merge request with at least 2 versions (pushes)
2. Select a version that is not the latest one
3. Copy a direct link to one of the diff lines in a file (not the current page URL)
4. Open that link in a new tab
5. The version of the MR should be correct