agl-image-minimal is not minimal (packages, defined users)

When building agl-image-minimal, the resulting image contains extra packages and users that shouldn't be included in the minimal images (for example: graphics stack = wayland, mesa ... and for users: xuser, mosquitto ...)

This has been observed on m3ulcb builds as well as qemu builds but all platforms may be affected (so I check all of them in this ticket)