Adjust roles parsing

[Paultagoras]

Summary

• Tweaks token generator to go character-by-character rather than regex (so it can account for double quotes)
• Expands tests to add additional roles

Checklist

Delete items not relevant to your PR:

• Closes issue
• 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

[sonarqubecloud]

Quality Gate failed

Failed conditions
78.4% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud