Implement iteration over more polynomial rings

[user202729]

Allows iterating over e.g. ℤ[x].

Improvement over #39399 in that it supports the case where the base ring is infinite as well.

📝 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

A lot of scaffoldings are needed. To view only the important changes of this pull request, see the last commit bc5c6c1#diff-3a235333ab35f6e289f75049a0e92cdfe4148c457aa30df91c2f6f174a90ecb3

• Implement iteration over some polynomial rings #39399
• Implement correct iteration through disjoint enumerated set for infinite set #39443
• Improve is_empty and is_finite in a few cases #39444

[github-actions]

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