Dagger, meet Flows. Flows, meet Dagger.

Daggerizes all of the EPP flows. This does not change anything yet
about the flows themselves, just how they are invoked, but after
this CL it's safe to @Inject things into flow classes.
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=125382478

java/google/registry/flows/host/HostDeleteFlow.java

@@ -36,6 +36,8 @@ import google.registry.model.host.HostResource;
 import google.registry.model.host.HostResource.Builder;
 import google.registry.model.reporting.HistoryEntry;
 
+import javax.inject.Inject;
+
 /**
  * An EPP flow that deletes a host resource.
  *
@@ -49,6 +51,8 @@ public class HostDeleteFlow extends ResourceAsyncDeleteFlow<HostResource, Builde
   /** In {@link #isLinkedForFailfast}, check this (arbitrary) number of resources from the query. */
   private static final int FAILFAST_CHECK_COUNT = 5;
 
+  @Inject HostDeleteFlow() {}
+
   @Override
   protected boolean isLinkedForFailfast(final Ref<HostResource> ref) {
     // Query for the first few linked domains, and if found, actually load them. The query is