Use SSPRK Solvers in the SplitExplicitSolver

[blallen]

Description

We would like to be able to use SSRPK solvers with the SplitExplicitSolver introduced in #1257. How much work is it to adapt this method to take both LSRK and SSRPK solvers as input? It's most important to have this flexibility with the slow method.

cc: @jkozdon @thomasgibson @christophernhill @jm-c

Additional context

Add any other reasons why this feature will help with the goals of CLIMA.

For CLIMA Developers

• This feature can be added (if it cannot be, explain why in a comment below -- lack of technical expertise, not relevant to the scope of this project, too ambitious)
• There is a timeline for when this feature can be implemented
• The feature has been (or will be) implemented (Please link the PR)