Options are now all global but may be overridden per-output. If an
output local value is requested but none has been set, the global value
is provided instead. This makes for much better ergonomics when
configuring layout related options in particular.
Replace the current layout mechanism based on passing args to a child
process and parsing it's stdout with a new wayland protocol. This much
more robust and allows for more featureful layout generators.
Co-authored-by: Isaac Freund <ifreund@ifreund.xyz>
