Context aware discussion navigation on diffs tab

What does this MR do and why?

Makes the discussion navigation on the diffs tab context aware

Screenshots or screen recordings

Screen_Recording_2022-10-10_at_16.01.38

How to set up and validate locally

1. Visit merge request diffs
2. Create comments on a diff in different on screen order
3. Navigate using discussion navigation buttons in the tab bar

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Closes #371557 (closed)