allow using empty local_suffix

[sergeykuprikov]

Summary

Allow empty local_suffix in configuration

Remove restriction that required non-empty local_suffix values.
Users can now use empty string for simpler configuration setups.

Checklist

Delete items not relevant to your PR:

• Unit and integration tests covering the common scenarios were added
• A human-readable description of the changes was provided to include in CHANGELOG
• For significant changes, documentation in https://github.com/ClickHouse/clickhouse-docs was updated with further explanations or tutorials

[CLAassistant]

All committers have signed the CLA.

[windsurf-bot]

Looks good to me 🤙

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[sergeykuprikov]

/windsurf-review

[windsurf-bot]

Looks good to me 🤙

💡 To request another review, post a new comment with "/windsurf-review".