Save the RDAP request time globally instead of passing it around

Also removed the rdapWhoisServer value, as it's just null and will likely stay that way (it isn't mentioned in the RDAP response profile)

If it'll ever become required, we can add it back.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=247643981

java/google/registry/request/RequestModule.java

@@ -17,6 +17,7 @@ package google.registry.request;
 import static com.google.common.net.MediaType.JSON_UTF_8;
 import static java.nio.charset.StandardCharsets.UTF_8;
 
+import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.VerifyException;
 import com.google.common.collect.ImmutableListMultimap;
 import com.google.common.io.ByteStreams;
@@ -47,6 +48,7 @@ public final class RequestModule {
   private final HttpServletResponse rsp;
   private final AuthResult authResult;
 
+  @VisibleForTesting
   public RequestModule(
       HttpServletRequest req, HttpServletResponse rsp) {
     this(req, rsp, AuthResult.NOT_AUTHENTICATED);