- [x] Have you signed the [CLA](http://www.ubuntu.com/legal/contributors/)? - [x] Have you added an entry to the changelog (`docs/reference/changelog.rst`)? ----- When a project indirectly depended on a plugin (e.g. the very common implicit dependency on Maven's "jar" plugin), Maven would use an internal hard-coded list of default version numbers to select what version to use, even if that version was not present. This PR changes the maven-use plugin to scan for all available Maven plugins on disk and add an explicit pin for every available plugin using `pluginManagement`, `pom.xml`'s equivalent to pip constraints. The main steps taken for this were: - Change the mapping of available Maven dependencies on-disk to also include the "packaging type" of each, which reveals if it is a plugin or not - Keep track of what plugins were an explicit dependency - For every plugin that was not an explicit dependency, but is found on disk, a `pluginManagement` entry is added instead - The integration test had the workaround for this bug removed in every file but one, which was kept to show either behavior works CRAFT-4590.