[DevTools] Move Timeline to footer instead of header

[sebmarkbage]

One thing that always bothered me is that the collapse buttons on either side of the toolbar looks like left/right buttons which would conflict with some steps buttons I plan to add. Another issue is that we'll need to add more tool buttons to the top and probably eventually a Search field. Ideally this whole section should line up vertically with the height of the title row.

I also realized that all UIs that have some kind of timeline control (and play/pause/skip) do that in the bottom below the content. E.g. music players and video players all do that. We're better off playing into that structure since that's the UI analogy we're going for here. Makes it clearer what the weird timeline is for.

By moving it to the bottom it also frees up the top for the collapse buttons and more controls.

Horizontal

Vertical

[MichaelSCollins]

Any way I can get paid to do some stuff here? lol

[eps1lon]

I like that. The filter toggle will look a bit lost once we get rid of the root switcher though.

[sebmarkbage]

We'll make it an icon and there will be more configs there as well.

I think we need the inspection button too so you can select on screen. Although that one in particular might go on the left.