Add MARBL Matrix Free Solve Test

[CRobeck]

We are interested in kernels for solving the advection equation: M[du/dt] = K u with DG-FEM.

We can break this up into two parts.

y = inv(M) x Since M is block diagonal we can look at applying a block diagonal matrix to a vector. Using hierarchical parallelism we can assign N number of blocks to a GPU thread block - N is a tunable parameter. The matrix block sizes are 27x27.

General question: Can we leverage the matrix cores for this?

2. Applying the action of K u Will be similar to the other FEM_PA kernels in the suite, will push up.

Something that can come from this is guide how we develop "tunable" kernels in general with RAJA.