SessionSetup conversion functions

[SebaLukas]

Todo:

• Adding missing conversion function in src/iso15118/message/session_setup.cpp
• Adding unit test to test the new conversion functions in test/exi/cb/iso20/session_setup.cpp

[cienporcien]

EV side conversions are added.

[SebaLukas]

The already existing Exi stream for the SessionSetupReq is unfortunately faulty. In this exi stream, the session ID length is zero. But it should be 8.
This would be the correct stream for the same SessionSetupReq message:

{0x80, 0x8C, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0D, 0x6C, 0xAC, 0x3A, 0x60, 0x62, 0x0B, 0x2B, 0xA6, 0xA4, 0xAB, 0x18, 0x99, 0x19, 0x9A, 0x1A, 0x9B, 0x1B, 0x9C, 0x1C, 0x98, 0x20, 0xA1, 0x21, 0xA2, 0x22, 0xAC, 0x00}

[cienporcien]

I used the basic config-sil-dc-d20.yaml along with the dsV2Gshark wireshark plugin to create new Exi streams for the unit tests, as well as the verbose dsV2Gshark message content for better documentation of the unit tests. Pull request created.

[cienporcien]

Also, I forgot, in order for the EV side conversions to work, this has to be added to variant.cpp:
} else if (doc.SessionSetupRes_isUsed) {
insert_type(va, doc.SessionSetupRes);