Configure index in @ParameterizedTest display names

This commit prepends "[{index}] " to all custom display names
configured via @ParameterizedTest.

This provides better diagnostics between the "technical names" reported
on the CI server vs. the "display names" reported within a developer's
IDE.

See gh-23451

spring-webflux/src/test/java/org/springframework/web/reactive/function/client/WebClientIntegrationTests.java

@@ -73,7 +73,7 @@ class WebClientIntegrationTests {
 
 	@Retention(RetentionPolicy.RUNTIME)
 	@Target(ElementType.METHOD)
-	@ParameterizedTest(name = "webClient [{0}]")
+	@ParameterizedTest(name = "[{index}] webClient [{0}]")
 	@MethodSource("arguments")
 	@interface ParameterizedWebClientTest {
 	}

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/SseIntegrationTests.java

@@ -65,7 +65,7 @@ class SseIntegrationTests extends AbstractHttpHandlerIntegrationTests {
 
 	@Retention(RetentionPolicy.RUNTIME)
 	@Target(ElementType.METHOD)
-	@ParameterizedTest(name = "server [{0}] webClient [{1}]")
+	@ParameterizedTest(name = "[{index}] server [{0}], webClient [{1}]")
 	@MethodSource("arguments")
 	protected @interface ParameterizedSseTest {
 	}

spring-webflux/src/test/java/org/springframework/web/reactive/socket/AbstractWebSocketIntegrationTests.java

@@ -80,7 +80,7 @@ abstract class AbstractWebSocketIntegrationTests {
 
 	@Retention(RetentionPolicy.RUNTIME)
 	@Target(ElementType.METHOD)
-	@ParameterizedTest(name = "client[{0}] - server [{1}]")
+	@ParameterizedTest(name = "[{index}] client[{0}], server[{1}]")
 	@MethodSource("arguments")
 	@interface ParameterizedWebSocketTest {
 	}