Fix Silo PBC logic

[markcmiller86]

Description

Resolves #20035

Still needs cleanup. I just wanted to get the working solution pushed.

Type of change

• [x] Bug fix~~
• [ ] New feature
• [ ] Documentation update
• [ ] Other

How Has This Been Tested?

Tested with material and contour plots on original dataset from @cyrush

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Checklist:

• [x] I have commented my code where applicable.~~
• [ ] I have updated the release notes.
• [ ] I have made corresponding changes to the documentation.
• [x] I have added debugging support to my changes.~~
• [ ] I have added tests that prove my fix is effective or that my feature works.
• [x] I have confirmed new and existing unit tests pass locally with my changes.~~
• [ ] I have added new baselines for any new tests to the repo.
• [x] I have NOT made any changes to protocol or public interfaces in an RC branch.~~

[markcmiller86]

I am running some of the plot's (Pseudocolor, Contour, FilledBoundary) through valgrind to ensure I haven't introduced any other funkiness to behavior. @cyrush if you have other suggestions for further testing, lemme know.

[markcmiller86]

Ok, I've run Psuedocolor, FilledBoundary, and Contour with MPI+valgrind and got no errors! I am seeing leaks though but I suspect that has to do with the fact that the engine generally doesn't try to clean up after itself when exiting. I will confirm that though.