Add GCF integration tests

Add Integration Tests for GcfSpringBootHttpRequestHandler2

fix up

fix build

cleanup after merge

Added process-based server integration test support

some more refactoring

remove unneeded maven deps

address Dmitry and Dans feedback

spring-cloud-function-adapters/spring-cloud-function-adapter-gcp/pom.xml

@@ -42,6 +42,11 @@
 			<artifactId>spring-boot-starter-test</artifactId>
 			<scope>test</scope>
 		</dependency>
+		<dependency>
+			<groupId>org.springframework</groupId>
+			<artifactId>spring-web</artifactId>
+			<scope>test</scope>
+		</dependency>
 		<dependency>
 			<groupId>com.google.cloud.functions.invoker</groupId>
 			<artifactId>java-function-invoker</artifactId>