Refactors RedisVectorStore to use the builder pattern for improved
configuration and usability. The changes include:
* Move classes to org.springframework.ai.vectorstore.redis package
* Add RedisBuilder with comprehensive configuration options
* Deprecate RedisVectorStoreConfig in favor of builder pattern
* Enhance documentation with detailed usage examples
* Improve error handling and parameter validation
This change makes RedisVectorStore configuration more intuitive and
consistent with other vector stores in the project.
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