Review Board 4.0 introduced a new set of CSS component classes for

sidebars and page sidebars. In the process, it tried to provide

compatible styling for the legacy #page_sidebar element, which may be

used in some extensions (and in fact is used in Power Pack).
This didn't end up looking right, though. The page sidebar was lacking

some crucial positioning and padding, and this broke the Power Pack

Reports pages and likely any other extensions that might be using this.
This change adds some of the important legacy styles back. We're

hard-coding some positioning values, rather than using any existing

variables for these, because we want to ensure the layout is as close to

3.0's styles as possible, in order to ensure these pages won't break in

other subtle ways.

Tested all the Power Pack 3 Reports pages and verified that layout was

correct once again.