Make cold storage and retention addons fully compatible

Currently, when content is under retention, it is not possible to send it to cold storage and vice versa.

This is a major limitation for ECM customers. Most of their content needs to be put under retention for legal reasons, and they want to use cold storage in order to optimize costs while this content is kept around but not used.

The goal of this epic is to make these two addons work together:

• allow to send content under cold storage when under retention
• allow to put content under retention when it is already sent into cold storage

These actions should be made possible while keeping the expected experience and compliance to the SEC-17A4 regulation.