Fixes for ALM restart

[marchdf]

Summary

Fixes for ALM restart:

1. ensure the root proc is set right after regrid restart
2. if restarting from a different directory, recreate the fast_velocity_data files

Pull request type

Please check the type of change introduced:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

Checklist

The following is included:

• new unit-test(s)
• new regression test(s)
• documentation for new capability

This PR was tested by running:

• the unit tests
  • on GPU
  • on CPU
• the regression tests
  • on GPU
  • on CPU

Additional background

This basically recomputes the root_proc for the actuators if they are not valid. Which can happen on restart when post_regrid gets called. We have to do it this way because determine_influenced_procs needs a valid mesh at all levels (to make the intersections with the box array) and it needs (for turbine fast) a valid root proc. We can't just call determine_root_proc for the actuator (we need to call the plain utils version) because, as stated in a TODO comment in there, that function actually does much more, including initializing the openfast instance. Quite the cluster.

Closes #1385

[marchdf]

Everything looks pretty good.
turbines.pdf