feat: add 'how=' to ak.unzip

[pfackeldey]

Closes #3582

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.65%. Comparing base (b749e49) to head (c7371b9).
⚠️ Report is 427 commits behind head on main.

Files with missing lines	Patch %	Lines
src/awkward/operations/ak_unzip.py	66.66%	3 Missing ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
src/awkward/operations/ak_unzip.py	90.00% <66.66%> (-6.16%)	⬇️

... and 196 files with indirect coverage changes

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[github-actions]

The documentation preview is ready to be viewed at http://preview.awkward-array.org.s3-website.us-east-1.amazonaws.com/PR3655

[ianna]

@pfackeldey - Great! Thanks!