This enables changing monitor settings for each monitor individually.
In the event that changing a resolution causes screens to overlap we
now try to disperse the screens, although the algorithm currently
implemented may result in some rather unexpected layouts in certain
cases. We can still improve this logic, and eventually we're going to
have a widget where the screens can be arranged as desired.
This sets the stage so that DisplaySettings can configure the screen
layout and set various screen resolutions in one go. It also allows
for an easy "atomic" revert of the previous settings.
This allows WindowServer to use multiple framebuffer devices and
compose the desktop with any arbitrary layout. Currently, it is assumed
that it is configured contiguous and non-overlapping, but this should
eventually be enforced.
To make rendering efficient, each window now also tracks on which
screens it needs to be rendered. This way we don't have to iterate all
the windows for each screen but instead use the same rendering loop and
then only render to the screen (or screens) that the window actually
uses.
