Move servlet-api and jetty-schemas to jetty-bundle

Following framework upgrades to Jetty 12, the servlet-api and jetty-schemas JAR libraries can be relocated to the nifi-jetty-bundle NAR instead of the application lib directory.

NiFi 1.2.0 moved servlet-api and jetty-schemas to the root lib directory due to Jetty loading issues with the AnnotationConfiguration class. Jetty 12 logs an informational message when attempting to load the Logback ServletContainerInitializer, but does not have any runtime issues. NiFi uses a configured shutdown hook instead of the ServletContainerInitializer, so loading the Logback implementation is not required, allowing the servlet-api JAR to be relocated.