Default to writing out UVH5 files rather than UVFITS

[bhazelton]

Description

Changed the default output format to UVH5 rather than UVFITS, mostly because it doesn't require phasing. All formats are available, this just changes the default if nothing is set.

Motivation and Context

fixes #376

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Reference simulation update or replacement
• [ ] Documentation change (documentation changes only)
• [ ] Version change
• [ ] Build or continuous integration change

Checklist:

For all pull requests:

• [x] I have read the contribution guide.
• [x] My code follows the code style of this project.

Breaking change checklist:

• [x] I have updated the docstrings associated with my change using the numpy docstring format.
• [x] I have updated the documentation to reflect my changes (if appropriate).
• [ ] My change includes backwards compatibility and deprecation warnings (if possible).
• [x] I have added tests to cover my changes.
• [x] All new and existing tests pass.
• [ ] I have checked that I reproduce the reference simulations or if there are differences they are explained below (if appropriate). If there are changes that are correct, I will update the reference simulation files after this PR is merged.
• [ ] I have checked (e.g., using the benchmarking tools) that this change does not significantly increase typical runtimes. If it does, I have included a justification in the comments on this PR.
• [x] I have updated the CHANGELOG.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (61caa50) 99.50% compared to head (f6f87f8) 99.55%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #445 +/- ## ========================================== + Coverage 99.50% 99.55% +0.04% ========================================== Files 12 12 Lines 2240 2239 -1 ========================================== Hits 2229 2229 + Misses 11 10 -1 ```

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