Add options support to PostgresMlEmbeddingClient

- Add postgremaddmbedding adoc page.
- Auto-configuration:
  - add missing  boot-starter.
  - refactor autoconf class and properties to accomodate the PostgresMlEmbeddingOptions.
- PostgesMlEmbeddingClient
  - Add the (default) options field and remove old fields.
  - Implement default and request options merging.
  - Add tests for options and merging.
- Remove redundant code.
- Code style fixes.

models/spring-ai-transformers/src/main/java/org/springframework/ai/transformers/TransformersEmbeddingClient.java

@@ -340,4 +340,4 @@ public class TransformersEmbeddingClient extends AbstractEmbeddingClient impleme
 		return new DefaultResourceLoader().getResource(uri);
 	}
 
-}
+}