Align withBean methods with ApplicationContext

Rework `AbstractApplicationContextRunner.withBean` methods to
align signatures as much as possible with those provided by
the `ApplicationContext`.

Also update the implementation to use a dedicate member
variable rather than adding initializers.

Closes gh-16011

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/flyway/FlywayEndpointTests.java

@@ -41,7 +41,7 @@ public class FlywayEndpointTests {
 	private final ApplicationContextRunner contextRunner = new ApplicationContextRunner()
 			.withConfiguration(AutoConfigurations.of(FlywayAutoConfiguration.class))
 			.withUserConfiguration(EmbeddedDataSourceConfiguration.class)
-			.withBean("endpoint", FlywayEndpoint.class, FlywayEndpoint::new);
+			.withBean("endpoint", FlywayEndpoint.class);
 
 	@Test
 	public void flywayReportIsProduced() {