kcms: Add new 'Animations' KCM for animation speed and desktop effects
This KCM includes the animation speed setting from Workspace's General Behaviour, and any desktop effects that provide animations.
This is a port of work done on kwin (wayland) to kwin-x11, and includes other commits:
EffectsModel: Don't add duplicate effects
kcms/animations: Disable animations settings when animation speed is instant When animation speed is instant, regardless of whether these effects are loaded, they will respect the animation speed and do nothing anyway, so let's communicate that by disabling their controls.
kcms/effects & kcm/animations: Make effect config dialog modal
kcms/animations: Use fewer Kirigami FormLayouts There's no need to separate the slider and exclusive/other effects layouts, only the final layout due to the use of repeaters.