The idea of this BOM is to simplify the dependency management in plugins and modules.
- New BOM module in the jenkinsci/jenkins repository. We could have an external BOM, but it complicates the release management
- Move library definitions from Parent POM and Jenkins WAR to the BOM file
- Update WAR and Core components to use BOM
- Update plugin POM to optionally include BOM if possible (depending on jenkins.version)