Complex number support

Find this while implementing https://github.com/SciML/BoundaryValueDiffEq.jl/pull/258

This MWE is just proof of the idea and may not be meaningful, but I think it can still prove that the current DI lacks support for sparse Jacobian of complex numbers.

using ForwardDiff, DifferentiationInterface, SparseMatrixColorings, ADTypes
const DI = DifferentiationInterface
#backend = AutoForwardDiff() # this works
backend = AutoSparse(
    AutoForwardDiff(),
    sparsity_detector = ADTypes.KnownJacobianSparsityDetector(ones(3, 3)),
    coloring_algorithm = ConstantColoringAlgorithm(ones(3, 3), ones(Int64, 3))
)
u0 = [1.0; 0.0; 0.0] .+1im
jac_cache = DI.prepare_jacobian(nothing, similar(u0), backend, u0)

stack trace

ERROR: MethodError: no method matching DifferentiationInterfaceSparseMatrixColoringsExt.PushforwardSparseJacobianPrep(::DifferentiationInterface.BatchSizeSettings{…}, ::SparseMatrixColorings.ColumnColoringResult{…}, ::Matrix{…}, ::Vector{…}, ::Vector{…}, ::DifferentiationInterfaceForwardDiffExt.ForwardDiffTwoArgPushforwardPrep{…})

Closest candidates are:
  DifferentiationInterfaceSparseMatrixColoringsExt.PushforwardSparseJacobianPrep(::BS, ::C, ::M, ::S, ::R, ::E) where {BS<:DifferentiationInterface.BatchSizeSettings, C<:(AbstractColoringResult{:nonsymmetric, :column}), M<:(AbstractMatrix{<:Real}), S<:(AbstractVector{<:Tuple{Vararg{T, N}} where {N, T}}), R<:(AbstractVector{<:Tuple{Vararg{T, N}} where {N, T}}), E<:DifferentiationInterface.PushforwardPrep}
   @ DifferentiationInterfaceSparseMatrixColoringsExt ~/.julia/packages/DifferentiationInterface/bulUW/ext/DifferentiationInterfaceSparseMatrixColoringsExt/jacobian.jl:11

Stacktrace:
 [1] _prepare_sparse_jacobian_aux_aux(::DifferentiationInterface.BatchSizeSettings{…}, ::SparseMatrixColorings.ColumnColoringResult{…}, ::Vector{…}, ::Tuple{…}, ::AutoSparse{…}, ::Vector{…})
   @ DifferentiationInterfaceSparseMatrixColoringsExt ~/.julia/packages/DifferentiationInterface/bulUW/ext/DifferentiationInterfaceSparseMatrixColoringsExt/jacobian.jl:107
 [2] _prepare_sparse_jacobian_aux(::DifferentiationInterface.PushforwardFast, ::Vector{…}, ::Tuple{…}, ::AutoSparse{…}, ::Vector{…})
   @ DifferentiationInterfaceSparseMatrixColoringsExt ~/.julia/packages/DifferentiationInterface/bulUW/ext/DifferentiationInterfaceSparseMatrixColoringsExt/jacobian.jl:81
 [3] prepare_jacobian(::Nothing, ::Vector{…}, ::AutoSparse{…}, ::Vector{…})
   @ DifferentiationInterfaceSparseMatrixColoringsExt ~/.julia/packages/DifferentiationInterface/bulUW/ext/DifferentiationInterfaceSparseMatrixColoringsExt/jacobian.jl:49
 [4] top-level scope
   @ ~/Random/test2.jl:27
Some type information was truncated. Use `show(err)` to see complete types.

I believe the culprit is the annotation of the compressed matrix being too restricted in the SparseMatrixColorings extensions, I locally changed this into more generic ones and the errors are gone.

https://github.com/JuliaDiff/DifferentiationInterface.jl/blob/cc8818a2bb0fb3dab2abf29ba213f89213a8613a/DifferentiationInterface/ext/DifferentiationInterfaceSparseMatrixColoringsExt/jacobian.jl#L3-L33

Start with the MWE and the SparseMatrixColorings extension at DifferentiationInterface/ext/DifferentiationInterfaceSparseMatrixColoringsExt/jacobian.jl, especially lines 3-33. Inspect the compressed-matrix type annotations involved in PushforwardSparseJacobianPrep, then rerun the complex-valued prepare_jacobian example. Done means sparse Jacobian preparation accepts the shown complex input without the MethodError.