Add support for Elasticsearch version 7.10.*

Upgrade elasticsearch-rest-client to 7.10.1.

Add V7_10 to the version manager and use it for all the V7 tests.

Change-Id: Ifb941eea63b90e107ae37c6a08ab1815d6c0f22b

java/com/google/gerrit/elasticsearch/ElasticVersion.java

@@ -25,7 +25,8 @@ public enum ElasticVersion {
   V7_6("7.6.*"),
   V7_7("7.7.*"),
   V7_8("7.8.*"),
-  V7_9("7.9.*");
+  V7_9("7.9.*"),
+  V7_10("7.10.*");
 
   private final String version;
   private final Pattern pattern;