839: Misc LoRaWAN improvements r=lulf a=timokroeger
Trying too get `embassy-lora` running on a [LoRa-E5 Dev Board](https://wiki.seeedstudio.com/LoRa_E5_Dev_Board/).
I can see the join message arriving in the The Things Network console but the device does not receive the accept message yet.
Opening this PR anyway because I think there are some nice things to decouple the lora crate from the nucleo board.
`@lulf` Could you test if this PR breaks your LoRa setup? Marking as draft for the time being.
Co-authored-by: Timo Kröger <timokroeger93@gmail.com>
Co-authored-by: Ulf Lilleengen <lulf@redhat.com>
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