Freeze Ubuntu, Minor CI improvements

[Kichura]

1. Freezes Ubuntu to 22.04 to avoid possible OS-related problems,
2. Sets persist-credentials to false in checkout job to avoid exposing repo to greater risks than imagined,
3. Sets check-latest to true in java job so that the latest JDK is always fetched instead of re-using the image's version instead,
4. Drops the validation wrapper job in favor of setup-gradle as the latter already has a built-in validation system implemented,
5. Updates Gradle's terms-of-service texts to become terms-of-use instead,
6. Prevents the dependency submission workflow from running on forked repos as submitting snapshots are disabled there.

[AlexProgrammerDE]

LGTM! Thanks for the PR ❤️