[REGRESSION] Enable service tree in classic UI

[CCoupel]

cf: https://github.com/orgs/ManageIQ/discussions/23067

As a ex RedHater, specialized on Cloudform for 5 years, I use to manage services as hierarchical ones; based on the Peter's book documentation;
For exemple, let's say that we have a root service that represent a Project, deployed by a service item that do some global like managing GIT repository, and managing global quota resources
then as children, some services that represents the environments, which will manage access rights and subsequent quota, nsx and vlan managements.
And each have children other services that provision VMs+any ansible playbook services.
with such granularity, it become easy to manage scaleout and more.
Having a different visibility for project management, and increasing security between environment

This need can eventually be activated via an entry in the advanced feature file for exemple