Make editor base layout solution more robust

[gordlin]

Description

The current base layout solution requires hardcoded heights. This means that, if any of the components changes their height, the layout gets thrown around.

Notice the double scrollbar. The editor itself shouldn't have one, but since the height of the header isn't the hardcoded height, the layout breaks.

Is your feature request related to a problem?

With the current solution, if we want to change any of the main layout elements, we need to change the hardcoded heights every time.

Proposed solution

While keeping the same layout, refactor the current solution to be more robust. It shouldn't break if element heights change

Alternatives considered

CSS Grid might work.