Fix Intl.Collator compare declaration

[afurm]

Fixes #62048

Summary

• Model Intl.Collator#compare as a readonly function-valued property with this: void.
• Add a compiler baseline test covering direct bound-function usage, rejection of this-dependent replacements, and readonly assignment behavior.

Validation

• There is an associated issue in the Backlog milestone
• Code is up-to-date with the main branch
• Ran hereby runtests locally:
  • npx hereby runtests --tests=intlCollatorCompareAccessor --runner=compiler
  • npx hereby runtests --tests=localesObjectArgument --runner=compiler
• There are new or updated unit tests validating the change

AI Assistance

This PR was authored with assistance from OpenAI Codex.

[jakebailey]

I don't think we need a second PR for this: #62052

[afurm]

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[afurm]

Closing this because I noticed #62052 already covers #62048. Sorry for the duplicate.