Fixed extra margin when the merge request tabs are affixed

This was caused by some weird padding that was on the container & then
not correctly removed.

The fix involved removing the container from inside the tabs holder div
& then adding the widths through CSS depending on if fixed & whether the
parent is limited width or not.

In reality out container classes need to be fixed as it is getting pretty un-managable at the moment this should of been an easy fix, but in reality turned into something much harder.

Closes #26853

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Handle videos in:
- MD preview in notes: commit, issue/MR, MR diff
- New notes in: commit, issue/MR, MR diff
- Persisted notes in: commit, issue/MR, MR diff
Signed-off-by: NRémy Coutable <remy@rymai.me>

Add max-height to prevent images from displaying larger than the provided screen size.

Also fix a failing test and add a new one.