Mark the uber-jar as a multi-release jar if META-INF/versions/ exists in the generated jar

Fixes https://github.com/quarkusio/quarkus/issues/19991

The commit here introduces a change to mark a uber-jar as `Multi-Release: true` if the generated uber jar has a `META-INF/versions/` directory. The commit also contains a test which reproduces the issue and verifies this change.