feat(copy): add DATE_FORMAT / DATETIME_FORMAT / TIMESTAMP_FORMAT supp…

[KR-bluejay]

…ort for CSV (draft)

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Refer to a related PR or issue link (optional)

• Issue: Add date and timestamp format to COPY TO (CSV, JSON) #6287

What's changed and what's your intention?

Summary (mandatory):
This PR introduces support for temporal formatting options (DATE_FORMAT, DATETIME_FORMAT, TIMESTAMP_FORMAT) in the COPY TO statement for CSV exports.

Details:

• Added parsing of the new WITH options into CsvFormat.
• Forwarded these options to the Arrow CSV writer, enabling custom formatting of date/datetime/timestamp columns during export.
• Currently implemented only for CSV. JSON and Parquet are untouched.

Limitations / Open Questions:

1. Validation: Chrono patterns need validation. Existing to_date / to_char functions already handle this; we may want to reuse that logic.
2. JSON format: Arrow’s JSON writer does not currently support custom temporal formatting. Should we raise an error, ignore the option, or implement a fallback?
3. Datetime vs Timestamp: The current design keeps both options (DATETIME_FORMAT and TIMESTAMP_FORMAT), but their distinction might need clarification (especially since Arrow internally treats datetime as timestamp).

PR Checklist

Please convert it to a draft if some of the following conditions are not met.

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR requires documentation updates.
• API changes are backward compatible.
• Schema or data changes are backward compatible.