Improve tabbing order of the `Timeline` component

[oleksandr-danylchenko]

For more natural keyboard navigation across the Timeline component, I would suggest such order:

1. Main timeline tab stop
2. Left arrow (provide focus indication and the rollover text)
3. Right arrow (provide focus indication and the rollover text)
4. Any visible links in the currently-selected timeline item
5. The controls (zoom in, zoom out, back) in the lower part of the timeline
6. Timeline credits link

Because now it goes in this way:

1. Main timeline tab stop
2. Any visible links in the currently-selected timeline item
3. Left arrow (provide focus indication and the rollover text)
4. Right arrow (provide focus indication and the rollover text)
5. Timeline credits link
6. The controls (zoom in, zoom out, back) in the lower part of the timeline

https://user-images.githubusercontent.com/68850090/174779355-00ff45cd-56d9-4017-9214-46198e4c78d1.mp4

And for me, if I would be a keyboard navigation user, the ability to access next/prev before the slide links or the MenuBar controls before the Timeline credits would be convenient and intuitive

[JoeGermuska]

fixed with 8019670