fix default solver selection for CuSparseMatrix

[hexaeder]

This PR attempts to fix #827 . It requires a revert of #828 (PRed in #833)

This fixes mainly cache creaction problems. Now, based on whether CUDSS is loaded and whether a CSC or CSR matrix is provided it skips the cholesky and/or lu cache build.

Also changes the default solver logic:

• CuSparseMatrixCSR -> Krylov if CUDSS not loaded (warns once), LU otherwise
• CuSparseMatrixCSR -> Krylov (warns once about this)

It also adds some tests for the default solver choice before and after using CUDSS and fixes some missing import in the cuda tests.

Checklist

• Appropriate tests were added
• Any code changes were done in a way that does not break public API
• All documentation related to code changes were updated
• [-] The new code follows the
  contributor guidelines, in particular the SciML Style Guide and
  COLPRAC. (new code does, surruding code does not)
• Any new documentation only uses public API

Additional context

Add any other context about the problem here.