* Update actions in GitHub Actions workflows
This PR updates the various actions used in the existing GitHub Actions workflows.
- `ubuntu-18.04` → `ubuntu-latest`
- `actions/checkout@v1` → `v4`
- `actions/checkout@v2` → `v4`
- `actions/setup-java@v1` → `v4`
- `eskatos/gradle-command-action@v1` → `gradle/actions/setup-gradle@v4`
- `actions/upload-artifact@v1` → `v4`
* Regenerate the Gradle Wrapper jar
* Enable `fetch-tags` in `unit-tests.yml`
* Fetch the full Git history