Handle plugins imported as regular dependency that are not on maven central

[celcius112]

When a project imports a plugin as a regular dependency, for instance

implementation("org.unbroken-dome.gradle-plugins:gradle-testsets-plugin:2.1.1")

the tool will not find it's latest version since the plugin is kept on Gradle's plugin portal.

A probable solution would be to try finding the dependency on the plugin portal if not found on maven central.

[celcius112]

This problem is not as trivial as expected. A plugin found on the portal will have a name that is not necessarily related to its classpath dependency. For instance the docker-compose plugin has a plugin name com.avast.gradle.docker-compose, but a classpath dependency with group gradle.plugin.com.avast.gradle and name gradle-docker-compose-plugin. Maybe we'll need to retrieve more metadata from the plugin portal in order to be able to match the classpath dependency.