Implement SEP-1330: Elicitation Enum Schema Improvements #412

This is a tracking issue for implementation of SEP-1330.

Summary

This SEP improves enum schema definitions in elicitation by deprecating the non-standard enumNames property in favor of JSON Schema 2020-12 compliant patterns using oneOf with const and title. The Kotlin SDK needs to implement new schema types (UntitledSingleSelectEnumSchema, TitledSingleSelectEnumSchema, UntitledMultiSelectEnumSchema, TitledMultiSelectEnumSchema), extend ElicitResult to support string arrays in the content field for multi-select responses, and maintain backward compatibility with the deprecated enumNames approach while supporting the new standardized patterns.