Prefer re2 over java.util.regex

Java's stock regex implementation doesn't guarantee linear time
complexity which makes it a security liability.
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=121159875

java/google/registry/xml/BUILD

@@ -20,5 +20,6 @@ java_library(
         "//java/com/google/common/io",
         "//third_party/java/joda_time",
         "//third_party/java/jsr305_annotations",
+        "//third_party/java/re2j",
     ],
 )