Refactor/polish changes
- Rename the folder "clients" to "adapters" as suggested by different partners
- Rename NetworkManagementInterface to BaseNetworkClient (as commented, this function is not a Base Class abstract interface - like the one used in the EdgeCloud side. On the contrary, is just a base class that it's inherited by the adapters (oai, open5gs, open5gcore) in the case any specific-per core logic is needed).
- Improve README
- Delete unused files