SMP Version 2 Support

[SZenglein]

This library has been written primarily before zephyr started adapting and making changes to SMP. The primary change I can see is the return type if there is an error.

Since we don't assume a return type for any request, it could be as simple as defining new V2 responses that the user can deserialize into.

Tasks I see:

• Identify and define new "group error types"
• Check if we can support both versions in one type
• Check if we can automatically detect the version
• Deserialize payload based on SMP header version field

References:
https://docs.zephyrproject.org/latest/services/device_mgmt/smp_protocol.html