Reduce some test duplication by moving common classes to the main directory.

This allowed me to declare a test dependency on the servlet-3.0:testing directory.  (Test directories can't depend on other test directories.)

Still needed to copy over all the actual test classes because of how the test hierarchy is declared.

Author: tylerbenson

instrumentation/servlet/servlet-3.0/library/build.gradle.kts

@@ -5,6 +5,8 @@ plugins {
 dependencies {
   compileOnly("javax.servlet:javax.servlet-api:3.0.1")
 
+  testImplementation(project(":instrumentation:servlet:servlet-3.0:testing"))
+
   testLibrary("org.eclipse.jetty:jetty-server:8.0.0.v20110901")
   testLibrary("org.eclipse.jetty:jetty-servlet:8.0.0.v20110901")
   testLibrary("org.apache.tomcat.embed:tomcat-embed-core:8.0.41")