SMP Error Version 1 and 2 are not supported correctly

[JPHutchins]

See discussion here: #3 (comment)

If the response is SMP Version 1 then the enums are mcumgr_err_t. If it's SMP Version 2 then the current implementation is (maybe) correct.

Consider how an application layer (e.g. smpclient) may interact with the types but prioritize correctness with the spec and Zephyr implementation. https://github.com/intercreate/smpclient/blob/4942251bf4256643fd8878641aa08519a6693d9b/smpclient/generics.py#L17-L28

Would be a good opportunity to change V0 and V1 to V1 and V2 - this will be a breaking change - better now than never!

[JPHutchins]

Chose V0 and V1 because it matches the enums provided. The spec calls for 0 = Version 1 and 1 = Version 2 🤦