Add vertex ai autoconfig and spring boot

- Add Vertex AI Autoconfigurations for chat and embedding clients.
 - Factor out the embeding client dimensions() computation into an abstract parent AbstractEmbeddingClient.
 - Add ITs
 - Vertex dos.

embedding-clients/spring-ai-postgresml-embedding-client/src/main/java/org/springframework/ai/embedding/PostgresMlEmbeddingClient.java

@@ -6,7 +6,6 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
-import java.util.concurrent.atomic.AtomicInteger;
 
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
@@ -25,7 +24,7 @@ import org.springframework.util.StringUtils;
  *
  * @author Toshiaki Maki
  */
-public class PostgresMlEmbeddingClient implements EmbeddingClient, InitializingBean {
+public class PostgresMlEmbeddingClient extends AbstractEmbeddingClient implements InitializingBean {
 
 	private final JdbcTemplate jdbcTemplate;
 
@@ -35,8 +34,6 @@ public class PostgresMlEmbeddingClient implements EmbeddingClient, InitializingB
 
 	private final String kwargs;
 
-	private final AtomicInteger embeddingDimensions = new AtomicInteger(-1);
-
 	private final MetadataMode metadataMode;
 
 	public enum VectorType {
@@ -162,14 +159,6 @@ public class PostgresMlEmbeddingClient implements EmbeddingClient, InitializingB
 				Map.of("transformer", this.transformer, "vector-type", this.vectorType.name(), "kwargs", this.kwargs));
 	}
 
-	@Override
-	public int dimensions() {
-		if (this.embeddingDimensions.get() < 0) {
-			this.embeddingDimensions.set(EmbeddingUtil.dimensions(this, this.transformer));
-		}
-		return this.embeddingDimensions.get();
-	}
-
 	@Override
 	public void afterPropertiesSet() {
 		this.jdbcTemplate.execute("CREATE EXTENSION IF NOT EXISTS pgml");