Small: Default initialize `BndInfo.dir`

[BenWibking]

PR Summary

Default initializes the value of BndInfo.dir to X0DIR.

This fixes the sanitizer warnings that appear in https://github.com/parthenon-hpc-lab/parthenon/issues/1120.

PR Checklist

• [ ] Code passes cpplint
• [ ] New features are documented.
• [ ] Adds a test for any bugs fixed. Adds tests for new features.
• [ ] Code is formatted
• [x] Changes are summarized in CHANGELOG.md
• [ ] Change is breaking (API, behavior, ...)
  • [ ] Change is additionally added to CHANGELOG.md in the breaking section
  • [ ] PR is marked as breaking
  • [ ] Short summary API changes at the top of the PR (plus optionally with an automated update/fix script)
• [ ] CI has been triggered on Darwin for performance regression tests.
• [ ] Docs build
• [ ] (@lanl.gov employees) Update copyright on changed files