MCTP Control Protocol codec

[embediver]

Implementation of a codec for MCTP Control Protocol messages.

Support for the following messages was implemented:

• Get Endpoint ID
• Set Endpoint ID
• Get MCTP Version Support
• Get MCTP Message Type Support

To support this, types for command/completion codes, message header and payload, and message supporting types where implemented.

For encoding/decoding a codec trait was introduced.

On top of the unit tests an example application is provided, which supports the Set Endpoint ID message.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: embediver / name: Marvin Gudel (15b0694, 19cd834, 6a0feaf, 75f4a99, cfd6a85, d4df1f9)
• ✅ login: JonasLoeffelholz / name: Jonas Löffelholz (24cb708, 7127eb2)

[embediver]

Note: This is currently still a draft due to the following:

• Code documentation is still missing
• The example needs to be tested
  • Might require additional support of the Discovery Notify message
• This PR depends on Features for MCTP Control Protocol #15 which is still open

[embediver]

The example now sends a Discovery Notify message on the bus / serial line to announce itself.
The Discovery Notify has an empty message body, so this is also already supported by the library.

Unfortunately the mctpd tool that I planned to use as bus owner does not support Discovery Notify messages (yet).
I read through the spec, but the Discovery Notify seems to be the only specified way for a hot-plug device to announce itself (at least for serial transport).

[embediver]

I removed the Discovery Notify again and tested the example with mctpd by triggering the address assignment over the d-bus interface.

I added a readme in the example folder, which describes how the test can be performed.

[wmaroneAMD]

@embediver Let me know if I can merge this

[embediver]

Rebased onto main and fixed build for tests and standalone lib.

This PR should now be ready to be merged.