ISF point2D input type UI in VDMX

The way VDMX handles the values for XY inputs of ISFs (fx) is problematic. Rather than setting the value range of sliders in the UI to the values defined in the ISF’s JSON header, VDMX will initially normalize the envelop. This would be ok if it remained consistent, but as soon as the effect is active on a layer the values change to match the pixel dimensions of that layer (RENDERSIZE.xy). This makes it impossible to create marks on the sliders because the relative positions will change, and setting the envelop with a local preset on the slider doesn’t work.