FSI/Extloads Regression Test Creation

[ndevelder]

This may need to be here, or may be more suited to inclusion in Nalu-Wind regression tests, but we should really have testing coverage on the Exawind ExtLoads/FSI code pathway.

Challenges include:

• Current turbine meshes that use this pathway are huge. Can we develop a small mesh that will run (and not necessarily return accurate results) that is reasonable for reg test usage? Maybe a single blade? Maybe very under-resolved?
• OpenFAST is often changing, can we somehow minimize the challenges this test will cause if we stay on OpenFAST dev?