Load OS version from boot partition for greater compatibility

[dfunckt]

This also removes the runtime dependency to balena-sdk and changes the public API of configure and initialize to require a device type manifest as an argument.

Change-type: major

[dfunckt]

Hmm, making the tests pass is going to be tricky. The images shipped for the test suite are really old and don't have os-release on the boot partition. Should I fetch more recent ones? Or maybe add the file manually and commit (though what should its contents be)? Any ideas?

[pimterry]

I would manually edit them and try to make them representative. They're not actually real images anyway, they're manually edited ones, because otherwise the repo would be massive.

The other option ofc is that you could look at #26, but I suspect that's a fair bit more work.

[dfunckt]

@pimterry, I've updated the images by mounting their partitions and copying the file from /etc/os-release, so it's as accurate as it can get. Tests pass now, thanks :)

[pimterry]

Some small comments, but otherwise this looks like a nice simple fix.

Marking it as a major version bump so it's not picked up by really old CLIs which are probably used to provision old images which don't have os-release on the boot partition. (Please let me know if you think otherwise)

I think we can actually do this as a non-major bump, and it will improve things overall. The previous version was hacky and doesn't work in lots of cases, whilst this new version will work in a lot more cases. Also, if it doesn't work anywhere it's fine - we just configure for both, which is an acceptable result for old images, and shouldn't break anything anywhere. Happy to discuss, but personally I'd lean towards making this minor.