SaveAll on entities with embeddings should use bulk APIs/calls if available from provider

[bsbodden]

We primarily use https://docs.spring.io/spring-ai/reference/api/embeddings.html and many of the providers have bulk embedding APIs

See https://github.com/redis/redis-om-spring/blob/main/redis-om-spring/src/main/java/com/redis/om/spring/vectorize/DefaultFeatureExtractor.java for the single Entity instance approach