use the official Gradle GHA

[aSemy]

Use the official Gradle GitHub Action https://github.com/marketplace/actions/gradle-build-action

Two reasons:

1. I've noticed that the GitHub actions aren't always cached, and thus they take longer than necessary
2. Less configuration is needed

[aSemy]

I also changed ./gradlew test to ./gradlew check, because I noticed that the API dumps are not up to date. The apiCheck task will run if the check task runs, not test.

[Raibaz]

Thanks a lot, especially for spotting that we were doing gradle test rather than gradle check!