Use HttpMessageConverters in client and server config

This commit uses the new `HttpMessageConverters` class for the HTTP
client (`RestTemplate` and `RestClient`) and HTTP server support.

This effectively removes the duplication of classpath detection for
message converters in multiple places: clients, server and the multipart
converter itself.
Instead of creating multiple instances of the same converters, this
allows applications to share converter instances as much as possible for
better memory efficiency.

As a result, this change also deprecates configuration methods in the
MVC support that are superseded by the new methods introduced for
`HttpMessageConverters` support.

Closes gh-33894

spring-test/src/main/java/org/springframework/test/web/servlet/setup/RouterFunctionMockMvcBuilder.java

@@ -268,6 +268,7 @@ public class RouterFunctionMockMvcBuilder extends AbstractMockMvcBuilder<RouterF
 		}
 
 		@Override
+		@SuppressWarnings("removal")
 		protected void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
 			converters.addAll(messageConverters);
 		}

spring-test/src/main/java/org/springframework/test/web/servlet/setup/StandaloneMockMvcBuilder.java

@@ -470,6 +470,7 @@ public class StandaloneMockMvcBuilder extends AbstractMockMvcBuilder<StandaloneM
 		}
 
 		@Override
+		@SuppressWarnings("removal")
 		protected void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
 			converters.addAll(messageConverters);
 		}