Zephyr features support

[mlaz]

It's been observed that zephyr has an in-tree implementation of SMP.
This doesn't look like it is 100% compliant with this repo's implementation.
At least on the serial image management implementation I havent been able to get image uploads to work properly.
This said, we are looking to implement coredump and log mgmt(provided we can make FCB logging happen in zephyr).
Would be nice to sync with whoever is managing this from the zephyr side.

[mlaz]

@utzig @de-nordic

[de-nordic]

Some time ago we have moved the Zephyr fork of mcumgr into Zephyr and did a lot of re-factoring.
We have dropped TinyCBOR variant that was embedded into mcumgr and use zcbor now.

We have also changed the SMP protocol a little bit, calling it v2, where now there are two types of rc codes you can get, one for the SMP protocol problems and another for command execution problems.

The UART still should function properly as we are using the mcumgr-cli with it successfully.

Currently @nordicjm is the maintainer of MCUmgr subsystem within Zephyr.