This will help a lot with developing chromes for different UI frameworks
where we can see which helper classes and processes are really using Qt
vs just using it to get at helper data.
As a bonus, remove Qt dependency from WebDriver.
We were super inconsistent about this, with most "new" classes living in
the Ladybird namespace, while "old" ones were in the global namespace,
or even sitting in the Browser namespace.
Rather than set a hacky scale factor on our QIconEngine, just set the
icon size for the toolbar icons. This avoids the icons being
unnecessarily scaled in other places (i.e. the context menu).
Rather than render the icons to a 16x16 bitmap, keep them as vector
graphics and render them on request. This keeps the icons crisp on high
DPI displays.
