refactor(udf): remove `function_type` field previously used by Deno UDF

[stdrc]

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What's changed and what's your intention?

This PR removes the unused function_type field from all structures related to user-defined functions (#16263). runtime is kept because it seems to be more general, so may be useful in the future.

Checklist

• [ ] I have written necessary rustdoc comments
• [ ] I have added necessary unit tests and integration tests
• [ ] I have added test labels as necessary. See details.
• [ ] I have added fuzzing tests or opened an issue to track them. (Optional, recommended for new SQL features #7934).
• [ ] My PR contains breaking changes. (If it deprecates some features, please create a tracking issue to remove them in the future).
• [x] All checks passed in ./risedev check (or alias, ./risedev c)
• [ ] My PR changes performance-critical code. (Please run macro/micro-benchmarks and show the results.)
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Documentation

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Release note

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[stdrc]

• #19404 👈 (View in Graphite)
• main

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