[console] bad layout css causes jankyness

It's very easy to get annoyed when using the console, because the console is very janky, i.e. when scrolling up and down, you sometimes get stuck in smaller blocks that scroll.

This is something that's not supposed to happen if you write good css; so I had look at the css and sorted out the start screen and data screen (to start with)

All in all, this case-base is *really really* in need of spring cleaning, including #8390 and #8391.

Start by reproducing the console scrolling problem, comparing the start screen and data screen mentioned in the issue. Inspect their CSS and determine which layout rules create nested or constrained scrolling; done means scrolling is smooth in both screens without getting stuck in smaller blocks. Review related issues #8390 and #8391 for context.

Written by the indexing model from the issue text.