446944 - ServletTester and HttpTester should be in <classifier>tests</classifier>

Moving HttpTester to "tests" scoped jetty-http artifact.

 + HttpTester, a testing class, was used by jetty-servlets,
   embedded-jetty-examples, and test-integration, all from
   those testing scopes.  Moved the HttpTester into the
   pre-existing jetty-http "tests" classified artifact.

Moving ServletTester to "tests" scoped jetty-servlet artifact.

 + ServletTester, a testing class, was used by jetty-servlets,
   test-integration, and test-jetty-webapp.  This move puts
   this class in the pre-existing jetty-servlet "tests" classified
   artifact.