Set up prepare_boundaries as a step prior to ApplyPredictor

[mbkuhn]

Summary

In order to accommodate the boundary plane implementation and correctly fill physical boundary cells at the right times, this PR sets up a framework to call "fill_boundaries" prior to the ApplyPredictor step, which enables avoiding calling fills at older times (n, n+1/2) once the time step has begun. With all of this new code, this PR is set up to avoid diffs, ensuring the framework does not do something unintentionally. Future PR will introduce diffs by filling BCs at the desired times, instead of conforming to the times the code currently uses.

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

The "no diffs" component of development intended by #1210.

The commit to main has the wrong name of the function. Should be "prepare_boundaries" instead of "fill_boundaries"

[marchdf]

I am seeing this:

The following tests FAILED:
          7 - abl_godunov_mpl (Failed)
          8 - abl_godunov_mpl_amr (Failed)
         87 - rankine (Failed)
         88 - rankine-sym (Failed)
         92 - freestream_godunov_inout (Failed)
        123 - abl_bndry_input_amr_native_xhi (Failed)
        124 - abl_bndry_input_amr_native_mlbc (Failed)
        128 - abl_bndry_input_amr_inflow (Failed)

I think we might expect the MPL ones? What about the others?

[marchdf]

Ok now seeing this:

The following tests FAILED:
          7 - abl_godunov_mpl (Failed)
          8 - abl_godunov_mpl_amr (Failed)
        123 - abl_bndry_input_amr_native_xhi (Failed)
        124 - abl_bndry_input_amr_native_mlbc (Failed)
        128 - abl_bndry_input_amr_inflow (Failed)

[marchdf]

We are at:

The following tests FAILED:
          7 - abl_godunov_mpl (Failed)
          8 - abl_godunov_mpl_amr (Failed)

which is good news. Let's do this.