Add support for SUNDIALS CUDA features. These changes will be easily
extendable to support future GPU features in SUNDIALS, e.g. HIP
features. To keep things clean, this creates a SundialsNVector
class to interface with the SUNDIALS N_Vector. This class inherits
from the mfem::Vector class, and follows the pattern used in MFEM
interfaces to other libraries such as PETSc and hypre.
The fix in example 9 uses the approach used in the regular
example 9 to fix the same leak (see PR #816).
Fix a memory leak in SUNDIALS example 9 using the same fix
that was used
Tzanio