Rework `hasAccelerator()` to require types instead of instances

[fwege]

The current implementation of hasAccelerator() requires the creation of an istance of type T <: AbstractAccelerator.
As the default constructor of CUDAccelerator() creates an instance of CuDevice() this is only possible if CUDA Drivers are available...
https://github.com/RWTH-ACS/CAMNAS.jl/blob/main/src/mna_solver.jl#L310-L313

function has_accelerator(accelerator::T) where T <:AbstractAccelerator
    global accelerators_vector
    findfirst(x -> typeof(x) == typeof(accelerator), accelerators_vector) !== nothing
end

FIx: We shoud modify hasAccelerator() to require types, not instances of accelerators.

Originally posted by @fwege in #19