Resolve node.js actions deprecation, Avoid chmod

[Kichura]

1. Updates checkout, setup-java and upload-artifact to resolve the deprecation warning when viewing actions overview, (wrapper validation is to be fixed)
2. Removes the chmod +x gradlew statement as we do not need this,
3. Adds the Gradle wrapper validation step to let this repo know if the uploaded jar is valid or not,
4. Upstreams the gradlew scripts.

(Please consider syncing this, should this be merged)

[FlashyReese]

LGTM!