Remove unused and misused methods from EppResourceUtils and DomainBase.

The methods in DomainBase were the only callers for the methods in
EppResourceUtils, so I first inlined them. Then I realized that there
were no callers for loadReferencedContacts() anywhere. For loadNameservers(),
all but one invocation actually wanted to load the foreign keys, and was
repeating that work, so I replaced it with loadNameserverFullyQualifiedHostNames().
The last invocation, in the Rdap code, was incorrectly assuming this was an async
load when in fact it blocks, so I replaced it with a real async load.
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=122433897

java/google/registry/tools/GenerateDnsReportCommand.java

@@ -104,12 +104,8 @@ final class GenerateDnsReportCommand implements RemoteApiCommand, GtechCommand {
     }
 
     private void write(DomainResource domain) {
-      ImmutableList<String> nameservers = FluentIterable.from(domain.loadNameservers())
-          .transform(new Function<HostResource, String>() {
-              @Override
-              public String apply(HostResource host) {
-                return host.getForeignKey();
-              }})
+      ImmutableList<String> nameservers = FluentIterable
+          .from(domain.loadNameserverFullyQualifiedHostNames())
           .toSortedList(Ordering.natural());
       ImmutableList<Map<String, ?>> dsData = FluentIterable.from(domain.getDsData())
           .transform(new Function<DelegationSignerData, Map<String, ?>>() {