TEX11 — Circular Dependency Between Group and Entity Payload packages

There is a circular dependency between the EntityPayload and GroupPayload packages. In particular this causes an issue with PSM generation.

GroupPayload package contains GroupPayload class which depends on EntityRef which is in the EntityPayload package. This is as per design.
EntityPayload package contains ExtendedData which depends on ExtensionSchema which is in GroupPayload package (and it is used in the GroupMetaData class). This is not intended.

Move ExtensionSchema to the Utils package.

The ExtensionSchema class is a general utility class, so can be moved to the utils package.