Image is now based on nrfutil toolchain-manager

[coderbyheart]

980ea41 changes the docker image to use nrfutil toolchain-manager to set up the build environment.

Because toolchain-manager is not available for nRF Connect SDK version below 2, the support for those versions of is dropped.

Reminder

The purpose of this project is not to provide stable images, but replicate what users are facing when they start developing with nRF Connect SDK (which itself does not provide a reproducible build environment).

If you want stable Docker images, use the Dockerfile in this repository as an example to build your own Docker image.

[coderbyheart]

Contributed a PR to the ZSWatch repo which got broken because of the image changes. This PR can be used as a reference if you MUST use the image directly.