Isolate customizable code in activity reporting

Modularize the code for DNS count reporting to allow it to be customized for
more flexible systems.
Tested:
  Uploaded to alpha with hacks to allow admin initiating and logging from the
  DnsCountQueryCoordinatorModule, verified that the provider function is invoked and
  that the action runs successfully.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=225225587

java/google/registry/config/RegistryConfigSettings.java

@@ -77,6 +77,7 @@ public class RegistryConfigSettings {
     public String customLogicFactoryClass;
     public String whoisCommandFactoryClass;
     public String allocationTokenCustomLogicClass;
+    public String dnsCountQueryCoordinatorClass;
     public int contactAutomaticTransferDays;
     public String greetingServerId;
     public List<String> registrarChangesNotificationEmailAddresses;