Refactor EppXmlTransformer to be in the model/ package

This will allow us to perform the OT&E history verification
in the model/ package as well so that it can be used both
by both the UI and the command line tool.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=225007167

javatests/google/registry/flows/session/LoginFlowTestCase.java

@@ -45,7 +45,7 @@ public abstract class LoginFlowTestCase extends FlowTestCase<LoginFlow> {
 
   @Before
   public void initRegistrar() {
-    sessionMetadata.setClientId(null);  // Don't implicitly log in (all other flows need to).
+    sessionMetadata.setClientId(null); // Don't implicitly log in (all other flows need to).
     registrar = loadRegistrar("NewRegistrar");
     registrarBuilder = registrar.asBuilder();
   }