Spring-ai Add Auto-Configurations and Boot starters for all Vector Store implementations

Most Spring-ai vector store implementations already have a proper boot auto-configurations in place. Create the corresponding Spring Boot Starters under the spring-ai-spring-boot-starters and update the VectorStore's README.md with both starter usage instructions.

• [x] Milvus Vector Store, using the milvus auto-configure
• [x] Chroma Vector Store, using the chroma auto-configure
• [x] PgVector Vector Store, using the pgvector auto-configure
• [x] Pinecone Vector Store, using the pinecone auto-configure
• [x] Azure Vector Store, using the azure vector store auto-configure
• [x] Weaviate Vector Store - using the weaviate vector store auto-configure
• [x] Redis Vector Store - using the redis vector store auto-configure
• [x] Neo4j Vector Store - using the neo4j auto-config

Comment From: tzolov

with the completion for neo4j, now all vector stores have auto-configurations and boot starters.