Sw version based downgrade prevention

[mateo-ligne-netatmo]

Hello everyone,

This PR follow a previous issue where I express my need of having a software version comparison before loading a new firmware through Recovery uart in a Single application slot configuration.

The firmware update will be monitored by MCUmgr, and in order to stop the update from it, I defined a new error type that will stop update process. This MCUmgr feature is the following open PR

I also added a commit allowing to use 2 UART peripheral at the same time one for Logs and the other for MCUmgr communication.

It's my first MCUBoot upload so don't hesitate to make feedbacks or suggestions, I will take them into account !

[mateo-ligne-netatmo]

Hello, I have rebased my PR with current MCUboot main especially following https://github.com/mcu-tools/mcuboot/pull/1255. It turns out that on a failed firmware update (for too low SW version for instance), stored binary won't be overwritten but it will be decrypted a second time which will break the applicative. To counter that, I've just had a return code check before decryption.

[d3zd3z]

I believe @utzig concerns have been addressed.

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