Refactor most of OT&E verification code to exist in utils class

This does not change existing functionality but will allow us to use this common code in the yet-to-be-created web console action as well.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=227159346

java/google/registry/model/OteAccountBuilder.java

@@ -361,7 +361,7 @@ public final class OteAccountBuilder {
   }
 
   /** Returns the ClientIds of the OT&E, with the TLDs each has access to. */
-  private static ImmutableMap<String, String> createClientIdToTldMap(String baseClientId) {
+  static ImmutableMap<String, String> createClientIdToTldMap(String baseClientId) {
     checkArgument(
         REGISTRAR_PATTERN.matcher(baseClientId).matches(),
         "Invalid registrar name: %s",