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

third_party/java/re2j/BUILD

@@ -0,0 +1,8 @@
+package(default_visibility = ["//visibility:public"])
+
+licenses(["notice"])  # BSD
+
+java_library(
+    name = "re2j",
+    exports = ["@re2j//jar"],
+)