Always prefix users and groups in schema properties

Today, when creating a schema property that can store either users or groups, Nuxeo will store the username or group name without any kind of identifier.

This can create a collision when users and groups are named the same.

Now that content needs to be kept in sync with Hx Insight and explicitly annotated, we need to make sure that there is a way to differentiate users and groups when storing this information.

AC:

• Users are stored with a "user:" prefix within a schema
• Groups are stored with a "group:" prefix within a schema
• If this behavior creates a breaking change, it is enabled through a configuration property, disabled by default in LTS 2023, enabled by default in LTS 2025