Add “policy_manager” , “reports_manager” and “watch_manager” to platform_group

[jfsarang]

Is your feature request related to a problem? Please describe.
The platform_group doesn't contain policy_manager, reports_manager, watch_manager, just like what artifactory_group used to have.

Describe the solution you'd like
This platform_group utilizes Group V2 REST API, which doesn't cover these properties like what we used to have with Security API. Once the properties are added to Group V2 REST APIs, platform_group should honor policy_manager, reports_manager, and watch_manager.