future proofing the post_process method to account for missing zero frequency in wave

[dtgaebe]

I received FutureWarnings during the merge in post_process.
The wave is always missing the zero frequency.

There is a simple fix:
join="outer" keeps the union of frequency values
compat='no_conflicts': allows “fill in missing” but no contradictions.

Further,
ifd.expand_dims({'realization':[ires]})
itd.expand_dims({'realization':[ires]})
did nothing.

Now changed so that the dimension is added before the concatenation (the concatenation actually expanded the dims)

Description

Concise description of the pull request with references to any issues.

Type of PR

• Bug fix
• New feature
• Documentation
• Other: (specify)

Checklist for PR

• Authors read the contribution guidelines
• The pull request is from an issue branch (not main) on your fork, to the dev branch in WecOptTool.
• The authors have given the admins edit access
• All changes adhere to the style guide including PEP8, Docstrings, and Type Hints.
• Modified the documentation if applicable
• Modified or added a new test
• All tests pass
• Reference or close any relevant issues

Additional details

Include any relevant context and describe any validation and verification efforts.

[coveralls]

Pull Request Test Coverage Report for Build 22323821097

Details

• 3 of 3 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 87.938%

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Totals
Change from base Build 22073734202:	0.0%
Covered Lines:	1254
Relevant Lines:	1426

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💛 - Coveralls

[jtgrasb]

This looks good and I confirmed it works locally for me. Ready to merge.