Tighten up restrictions on domain/host naming on EPP resources

All domain/host names should be stored in their canonical forms (puny-
coded and lower-cased). This validation is already in the flows, but
this adds protection against bad data from other sources, e.g. admin
consoles or RDE imports.

This also removes an old work-around that temporarily suspended this
validation for superusers, because we used to have non-canonicalized
data in the system. The non-canonicalized data has since all been
cleaned up, so this work-around is no longer necessary.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=146799558

javatests/google/registry/whois/NameserverWhoisResponseTest.java

@@ -59,7 +59,7 @@ public class NameserverWhoisResponseTest {
     createTld("tld");
 
     hostResource1 = new HostResource.Builder()
-        .setFullyQualifiedHostName("NS1.EXAMPLE.tld")
+        .setFullyQualifiedHostName("ns1.example.tld")
         .setCurrentSponsorClientId("example")
         .setInetAddresses(ImmutableSet.of(
             InetAddresses.forString("192.0.2.123"),
@@ -68,7 +68,7 @@ public class NameserverWhoisResponseTest {
         .build();
 
     hostResource2 = new HostResource.Builder()
-        .setFullyQualifiedHostName("NS2.EXAMPLE.tld")
+        .setFullyQualifiedHostName("ns2.example.tld")
         .setCurrentSponsorClientId("example")
         .setInetAddresses(ImmutableSet.of(
             InetAddresses.forString("192.0.2.123"),