Stop building internal images

Now that v2022 has moved to Bullseye running on the ancient 3.14 kernel used by the internal image is much more challenging.

The modern Bullseye userspace may fail due to missing syscalls, lack of features or bugs in seven-years-old kernels.

The internal images are now no longer representative of the usage of Apertis in that contenxt and alternative strategies that do not involve the custom images would be much more effective in actually producing value, so let's drop them from v2022.

This has been discussed and agreed in yesterday's grooming call.