Javadoc of library X version Y is published to https://google.github.com/tink/javadoc/X/Y. For example, Javadoc of the Android flavor HEAD-SNAPSHOT is https://google.github.com/tink/javadoc/tink-android/HEAD-SNAPSHOT.

To do this automatically, I had to change a few things:

* Adding gen_maven_jar_rules, replacing jarjar with java_single_jar.

* Moving RewardedAds to apps/rewardedads/src. Somehow if it's in apps/rewardedads/java, Bazel/Blaze would include src/main/java in the package name and break our Maven rules.

PiperOrigin-RevId: 190494835
GitOrigin-RevId: ec42c3cdca9742526afb077ef8cedcc8da38f46a