* WIP on separating out the OTA backends.
* Split off the individual OTA backends.
* Cleanup the three backends, split into .h and .cpp.
* After successfull flashing, activate the new boot partition.
* Fix linting issues.
* Minor cleanup
Co-authored-by: Maurice Makaay <mmakaay1@xs4all.net>
Co-authored-by: Otto winter <otto@otto-winter.com>