BB-common needs a dedicated migration doc

Motivation

Since bb-common has now evolved to include multiple resources, the minimal migration documentation in the network policies doc should be removed and a new migration doc should be created.

Acceptance Criteria

• The migration section of the bb-common netpol docs must be removed
• A new migration doc must be created
• The new doc must be structured in such a way that it can organically be expanded as new features are added to the bb-common chart