When focusing the main view, going into full screen mode by pressing '+' twice,
and then opening the search prompt ('/') or a menu (e.g. '?' or ':'), the full
screen display would switch to the focused side panel.
Fix this by always excluding popups from the window arrangement logic. No popup
should ever have any influence on how the views beneath it are laid out.
The output of the GetWindowDimensions function is hard to understand just by looking at it,
so I've added a helper function in the tests to render the window layout as text, so that
in order to create a new test you just come up with some args and paste the output as the
expected output.
This has the same downsides that any snapshot-based testing has: it's more brittle than
targeted assertions. But it is much easier to make sense of these snapshots than it is
to make sense of more fine-grained assertions, and I like the fact that these tests can
serve as documentation.
