Add `dolfinx.fem.LinearProblem` using SuperLU_Dist

[jhale]

Describe new/missing feature

I propose adding a new dolfinx.fem.LinearProblem class which exclusively uses the new built-in SuperLU_DIST solver interface. This would be a modification (and simplification, given the limited feature set of SuperLU_DIST) of the existing dolfinx.fem.petsc.LinearProblem class.

Suggested user interface

solver = dolfinx.fem.LinearProblem(a, L, superlu_dist_options={...})
u_h = solver.solve()