feat: add in-memory vector search plugin with multilingual support

[hgaol]

• Implemented the in-memory vector search functionality in the new vector-search-memory plugin.
• Added English and Chinese localization files for plugin configuration and descriptions.
• Created a comprehensive configuration structure for embedding API integration, including API host, key, model, level, and similarity threshold.
• Developed core functionalities for document management, including adding, updating, deleting, and searching documents based on cosine similarity.
• Introduced synchronization capabilities to bulk index questions and answers from the registered syncer.
• Embedded necessary metadata and logging for better traceability and debugging.