chore: refine quotation

[tianzhou]

Followup #178

[Copilot]

Pull request overview

This PR refines the quotation handling implementation by making the NeedsQuoting function private and removing redundant test cases. This is a follow-up to PR #178 that cleans up the API surface and eliminates test duplication.

Key changes:

• Made NeedsQuoting function private by renaming it to needsQuoting, as it's only used internally by QuoteIdentifier
• Removed the redundant TestNeedsQuoting test function, as the private function is fully tested through TestQuoteIdentifier
• Removed explicit reserved word test cases that were redundant with the dynamic test loop

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
ir/quote.go	Renamed NeedsQuoting to needsQuoting to make it a private function
ir/quote_test.go	Removed TestNeedsQuoting function and redundant explicit reserved word test cases from TestQuoteIdentifier

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[tianzhou]

@Adam-Mustafa