Create a load testing EPP client (#2415)

* Create a load testing EPP client.

This code is mostly based off of what was used for a past EPP load testing client that can be found in Google3 at https://source.corp.google.com/piper///depot/google3/experimental/users/jianglai/proxy/java/google/registry/proxy/client/

I modified the old client to be open-source friendly and use Gradle.

For now, this only performs a login and logout command, I will further expand on this in later PRs to add other EPP commands so that we can truly load test the system.

* Small changes

* Remove unnecessary build dep

* Add gradle build tasks

* Small fixes

* Add an instances setUp and cleanUp script

* More modifications to instance setup scripts

* change to ubuntu instance

* Add comment to make ssh work

config/presubmits.py

@@ -100,12 +100,12 @@ PRESUBMITS = {
                    {"node_modules/"}, REQUIRED):
         "Source files must end in a newline.",
 
-    # System.(out|err).println should only appear in tools/
+    # System.(out|err).println should only appear in tools/ or load-testing/
     PresubmitCheck(
         r".*\bSystem\.(out|err)\.print", "java", {
             "StackdriverDashboardBuilder.java", "/tools/", "/example/",
-            "RegistryTestServerMain.java", "TestServerExtension.java",
-            "FlowDocumentationTool.java"
+            "/load-testing/", "RegistryTestServerMain.java",
+            "TestServerExtension.java", "FlowDocumentationTool.java"
         }):
         "System.(out|err).println is only allowed in tools/ packages. Please "
         "use a logger instead.",