Check if `PointTypes` are ever interpolated onto another grid

[fhagemann]

We allow for mapping ScalarPotentials onto another Grid by interpolating between given potential values between grid points.
However, this makes no sense for PointTypes (even though the functionality exists).
https://github.com/JuliaPhysics/SolidStateDetectors.jl/blob/main/src/ScalarPotentials/ScalarPotential.jl#L19

We should cross-check that this is never used and maybe implement some safety measure to avoid this being used.