Convert Change.Id to AutoValue

See I6982fb24 for context.

Change-Id: I95de46939a11d9a6116680f5b881cdfcf6fe705a
diff --git a/java/com/google/gerrit/elasticsearch/ElasticChangeIndex.java b/java/com/google/gerrit/elasticsearch/ElasticChangeIndex.java
index f7edac2..38f8578 100644
--- a/java/com/google/gerrit/elasticsearch/ElasticChangeIndex.java
+++ b/java/com/google/gerrit/elasticsearch/ElasticChangeIndex.java
@@ -208,7 +208,7 @@
       int id = source.get(ChangeField.LEGACY_ID.getName()).getAsInt();
       // IndexUtils#changeFields ensures either CHANGE or PROJECT is always present.
       String projectName = requireNonNull(source.get(ChangeField.PROJECT.getName()).getAsString());
-      return changeDataFactory.create(Project.nameKey(projectName), new Change.Id(id));
+      return changeDataFactory.create(Project.nameKey(projectName), Change.id(id));
     }
 
     ChangeData cd =