[Feature]: Add "path" system column (fullpath of the parent)

[dkarlovi]

Feature description

Currently you can fetch fullpath which is path + key. But, for create mutation, you require path and key separately.

key can be fetched as a system column, we can obviously fetch fullpath and remove key, but for feature completeness it would make sense to also provide path as a separate system column.

[github-actions]

Thanks a lot for reporting the issue. We did not consider the issue as "Pimcore:Priority", "Pimcore:ToDo" or "Pimcore:Backlog", so we're not going to work on that anytime soon. Please create a pull request to fix the issue if this is a bug report. We'll then review it as quickly as possible. If you're interested in contributing a feature, please contact us first here before creating a pull request. We'll then decide whether we'd accept it or not. Thanks for your understanding.