GitLab

- Use `maven:3.8.1-openjdk-11` instead of custom image (OpenJDK 11 should fix SonarQube plugin execution issue).
- Add `-Dmaven.compiler.release=8` Maven CLI option to build jar files compatible with Java 8.

https://gitlab.ow2.org/ow2/oscar/xwiki/-/jobs/38252 reports:
```
Some files failed to scan properly:
Path: xwiki-platform/xwiki-platform-core/xwiki-platform-oldcore/target/site/jacoco/jacoco.xml
```

We don't want ScanCode to analyze build files.

- Comment out scancode and sonar for testing.
- Removre profiles: `integration-tests` and `docker` as we only want to run unit test not integration nor selenium.

Now trying to work from a custom docker image

Also try to remove build artifacts

 (yay!), now enabling the whole pipeline