Use meta-annotations on @AutoConfigureWebMvc to compose it with @AutoConfigureJson

[philwebb]

Currently @AutoConfigureWebMvc imports JSON auto-configuration directly. If we use @AutoConfigureJson then any user customizations to org.springframework.boot.test.autoconfigure.json.AutoConfigureJson.imports would be automatically picked up. We should review if the current arrangement is intentional and if we should switch.

[Wzy19930507]

@philwebb Hello may i pick it up, and also use meta-annotations on @AutoConfigureWebClient and @AutoConfigureJsonTesters to compose it with @AutoConfigureJson

@AutoConfigureJson
public @interface AutoConfigureJsonTesters {

[scottfrederick]

Closing in favor of #39253