Support embedded web environment with @AutoConfigureWebTestClient

Simplify `WebTestClient` testing support by removing the direct
context customizer in favor of using `@AutoConfigureWebTestClient`.

See gh-46356

Author: wilkinsona

core/spring-boot-test/src/main/java/org/springframework/boot/test/web/reactive/client/WebTestClientContextCustomizer.java

@@ -6,9 +6,8 @@ org.springframework.boot.test.context.filter.ExcludeFilterContextCustomizerFacto
 org.springframework.boot.test.context.filter.annotation.TypeExcludeFiltersContextCustomizerFactory,\
 org.springframework.boot.test.http.client.DisableReactorResourceFactoryGlobalResourcesContextCustomizerFactory,\
 org.springframework.boot.test.json.DuplicateJsonObjectContextCustomizerFactory,\
-org.springframework.boot.test.web.reactive.client.WebTestClientContextCustomizerFactory,\
 org.springframework.boot.test.web.servlet.client.RestTestClientContextCustomizerFactory
 
 # Application Context Initializers
 org.springframework.context.ApplicationContextInitializer=\
-org.springframework.boot.test.context.filter.ExcludeFilterApplicationContextInitializer
+org.springframework.boot.test.context.filter.ExcludeFilterApplicationContextInitializer

core/spring-boot-test/src/main/java/org/springframework/boot/test/web/reactive/client/WebTestClientContextCustomizerFactory.java

@@ -28,6 +28,7 @@ dependencies {
 	testImplementation(project(":module:spring-boot-http-codec"))
 	testImplementation(project(":module:spring-boot-restclient-test"))
 	testImplementation(project(":module:spring-boot-tomcat"))
+	testImplementation(project(":module:spring-boot-webflux-test"))
 	testImplementation(project(":module:spring-boot-web-server"))
 	testImplementation("io.projectreactor.netty:reactor-netty-http")
 	testImplementation("org.springframework:spring-webmvc")