Add GraphQlTest annotation

Prior to this commit, we could only test Spring GraphQL applications
with a complete application - all application and infrastructure
components were involved. While using `@SpringBootTest` is often useful
for complete integration tests (with or without a live running server),
we often want to write lean integration tests and test slices of our
application.

Just like `@WebMvcTest` or `@WebFluxTest`, this commit introduces the
support for `@GraphQlTest`. This annotation helps us to test a
particular slice of our application: a hand-picked selection of
`@Controller`, plus `RuntimeWiringConfigurer` and `WebInterceptor`
beans.

Other `@Component` must be imported or mocked for those tests.

This commit also refactors the existing auto-configuration to enable
this use case. The `WebGraphQlHandlerAutoConfiguration` now holds the
required components for `@GraphQlTest`, while other web-related
auto-configurations bring the web framework and transport
infrastructures.

Closes gh-75

samples/webmvc-http-security/src/test/java/io/spring/sample/graphql/SampleApplicationTests.java

@@ -4,7 +4,7 @@ import org.junit.jupiter.api.Test;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
 import org.springframework.boot.test.context.SpringBootTest;
-import org.springframework.graphql.boot.test.tester.AutoConfigureGraphQlTester;
+import org.springframework.graphql.boot.test.tester.AutoConfigureWebGraphQlTester;
 import org.springframework.graphql.execution.ErrorType;
 import org.springframework.graphql.test.tester.WebGraphQlTester;
 
@@ -13,7 +13,7 @@ import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
 @SpringBootTest
 @AutoConfigureMockMvc
-@AutoConfigureGraphQlTester
+@AutoConfigureWebGraphQlTester
 class SampleApplicationTests {
 
 	@Autowired