Parse info on DLT network trace frames and contained protocols

[kruss]

According DLT specification PRS_Dlt_00621 if the MSTP field is set to 0x2 (DLT_TYPE_NW_TRACE) the Message Type Info field (MTIN) will provide the type of the contained network protocol, which could be of kind:

• 0x1 (DLT_NW_TRACE_IPC)
• 0x2 (DLT_NW_TRACE_CAN)
• 0x3 (DLT_NW_TRACE_FLEXRAY)
• 0x4 (DLT_NW_TRACE_MOST)
• 0x5 (DLT_NW_TRACE_ETHERNET)
• 0x6 (DLT_NW_TRACE_SOMEIP)
• 0x7-0xF (User Defined)

The dlt-core library would need to return this information on parsing DLT-Frames, so a callee can further process the contained network trace payloads.

A possible implementation would be to extend the returned dlt::PayloadContent of parse::dlt_message with an enum-item NetworkTrace providing the possible network types.

As DLT network traces are flagged as non-verbose, but may contain several DLT payload arguments, the NetworkTrace items should already provide the list of the raw bytes of those arguments.