Simplify matrix construction in btquotient

[Eloitor]

Simplify matrix construction in btquotient.py to improve readability.

📝 Checklist

• The title is concise and informative.
• The description explains in detail what this PR is about.
• I have linked a relevant issue or discussion.
• I have created tests covering the changes.
• I have updated the documentation and checked the documentation preview.

⌛ Dependencies

[github-actions]

Documentation preview for this PR (built with commit 81ad425; changes) is ready! 🎉
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[user202729]

Hopefully no performance regression caused by column_matrix(). But probably negligible.

[Eloitor]

I'm generalizing this code for number fields, and simplifying the code will make it easier for me and reviewers