overset refactoring (UpdateGradP)

[mbkuhn]

Summary

This is part of a bigger effort for bringing features for overset multiphase into main. Also, this is a clearer way of labeling things that AMR-Wind needs to do when coupled to the overset solver.

• remove references to overset from incflo_advance
• put them in incflo instead
• UpdateGradP is only used in overset simulations, define it in OversetOps class
• move generic projection functions to header file, remove from incflo class

Pull request type

• [ ] Bugfix
• [ ] Feature
• [ ] Code style update (formatting, renaming)
• [x] 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
  • [x] on CPU
• the regression tests
  • [ ] on GPU
  • [x] on CPU

Additional background

Should be tested with regression tests

[mbkuhn]

this should also be tested with the regression tests from exawind-driver

[mbkuhn]

Confirmed that the regression tests (exawind-driver and amr-wind) both pass with the changes from this PR.