Context aware discussion navigation

What does this MR do and why?

Fixes “Jump to next unresolved thread” button should ... (#281947 - closed)

This MR adds visual context to the discussion navigation ().

That means it will respect your current view and will jump to the next or previous visible discussion.

Important: this MR does not address Changes tab discussion navigation since it uses completely different rendering mechanism.

Screenshots or screen recordings

Before	After

How to set up and validate locally

Open an MR that you own that has a few discussions and try to navigate through them using arrows on top or N and P keyboard keys.

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.