Move common duplicated code from plugins to pulpcore #7251
Description
The has_task_completed function is duplicated across at least the container plugin and the maven plugin
Significant portions of the Maven and Rust plugins contain similar-if-not-identical code for e.g. storing cached content
In any such cases it would make sense to put as much code as possible into Pulpcore rather than copy+paste between plugins
There are also conventions for things such as URL slugs, and domain handling, that could potentially be made more similar across plugins