Separate SDFs based on LightOccluder2D mask

[pmoosi]

It's currently possible to automatically create a signed distance field (SDF) in 2D by using LightOccluder2Ds and their sdf_collider property. The SDF can be used in custom shaders and for particle collisions.
This works well, but it has the downside of all occluders being part of the same SDF. This can make it impossible to use with multiple shaders or particle collisions that should only apply to a some occluders.

As an example I have a project where I use the SDF to cast drop shadows (as seen in #43886) and for particle collision with solid objects. I now have some 'glass' objects that should not cast a shadow but which should 'stop' particles. As it is currently, this is not possible with the built in SDF.

I'm wondering if it would be possible to create separate SDFs based on, e.g., the occluders' light mask. I have no idea if this is technically feasible, but it would make SDFs more versatile.