ARM image builds standardize on linux-omarchy

The quattro commit omacom/omarchy-iso@62d151d4d162, authored by emirb, makes linux-omarchy the only accepted kernel for aarch64 image builds. It removes the alternative Arch Linux ARM kernel path and its associated console, compression and device-tree handling.

The installer continues to install the kernel recorded by the image. The supplied event establishes a committed image-build change, rather than a released installation image.