Add WLS as a transport option for VNF/PNF, refactor existing options

This MR adds a new transport mechanism for the VNF and PNF split, using the Intel WLS library, which makes use of DPDK and shared memory to transport messages. This transport mechanism is what is used to interface with Radisys ODU, while also working with OAI VNF/PNF.

The VNF and PNF have been refactored so that the transport-specific functions are isolated from the rest of the logic, and as such, interchangeable by means of function pointers.

The same change is done for the packing/unpacking procedures, allowing to switch between FAPI and nFAPI encoding.

This MR also reduces the amount of duplicated code, by refactoring the VNF with Aerial, which now only has the transport-relevant functions, as well as the ones that are unique to it ( for example, the unpacking procedures where a secondary data buffer is used for the message payloads )

Additionally a new callback is added to the VNF to process ERROR.indication messages, which currently only indicates which message originated the error, and which error occurred.