Make built-in RetryPolicy implementations final

Closes gh-35040

spring-core/src/main/java/org/springframework/core/retry/support/MaxRetryAttemptsPolicy.java

@@ -27,7 +27,7 @@ import org.springframework.util.Assert;
  * @author Sam Brannen
  * @since 7.0
  */
-public class MaxRetryAttemptsPolicy implements RetryPolicy {
+public final class MaxRetryAttemptsPolicy implements RetryPolicy {
 
 	/**
 	 * The default maximum number of retry attempts: {@value}.

spring-core/src/main/java/org/springframework/core/retry/support/MaxRetryDurationPolicy.java

@@ -30,7 +30,7 @@ import org.springframework.util.Assert;
  * @author Sam Brannen
  * @since 7.0
  */
-public class MaxRetryDurationPolicy implements RetryPolicy {
+public final class MaxRetryDurationPolicy implements RetryPolicy {
 
 	/**
 	 * The default maximum retry duration: 3 seconds.

spring-core/src/main/java/org/springframework/core/retry/support/PredicateRetryPolicy.java

@@ -28,7 +28,7 @@ import org.springframework.core.retry.RetryPolicy;
  * @author Sam Brannen
  * @since 7.0
  */
-public class PredicateRetryPolicy implements RetryPolicy {
+public final class PredicateRetryPolicy implements RetryPolicy {
 
 	private final Predicate<Throwable> predicate;
 

spring-core/src/test/java/org/springframework/core/retry/RetryTemplateTests.java

@@ -20,7 +20,6 @@ import java.time.Duration;
 
 import org.junit.jupiter.api.Test;
 
-import org.springframework.core.retry.support.MaxRetryAttemptsPolicy;
 import org.springframework.util.backoff.FixedBackOff;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -110,20 +109,15 @@ class RetryTemplateTests {
 			}
 		};
 
-		MaxRetryAttemptsPolicy retryPolicy = new MaxRetryAttemptsPolicy() {
-			@Override
-			public RetryExecution start() {
-				return new RetryExecution() {
-
+		RetryPolicy retryPolicy = () -> new RetryExecution() {
 			int retryAttempts;
 
 			@Override
 			public boolean shouldRetry(Throwable throwable) {
-						return this.retryAttempts++ < 3 && throwable instanceof TechnicalException;
-					}
-				};
+				return (this.retryAttempts++ < 3 && throwable instanceof TechnicalException);
 			}
 		};
+
 		retryTemplate.setRetryPolicy(retryPolicy);
 		retryTemplate.setBackOffPolicy(new FixedBackOff(Duration.ofMillis(10)));