Properly handle NAME_COLLISION domains in start-date sunrise

Domains that are reserved with type NAME_COLLISION can be registered defensively
during sunrise only, but DNS can never resolve for them. Correspondingly, we
need to apply the SERVER_HOLD status for such registrations. We also send the
registrar a poll message informing them of this act.

This brings us up to feature parity with end-date sunrise (implemented in
DomainAllocateFlow), which already has all of this handling.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=205277728

java/google/registry/flows/domain/DomainFlowUtils.java

@@ -149,6 +149,12 @@ public class DomainFlowUtils {
           ReservationType.NAME_COLLISION,
           ReservationType.MISTAKEN_PREMIUM);
 
+  /** Warning message for allocation of collision domains in sunrise. */
+  public static final String COLLISION_MESSAGE =
+      "Domain on the name collision list was allocated. But by policy, the domain will not be "
+          + "delegated. Please visit https://www.icann.org/namecollision  for more information on "
+          + "name collision.";
+
   /** Non-sunrise tld states. */
   private static final ImmutableSet<TldState> DISALLOWED_TLD_STATES_FOR_APPLICATION_FLOWS =
       Sets.immutableEnumSet(