Draft: Sync create-homedir-if-needed with the duplicate in apertis-image-recipes

At some point {chaiwala,apertis}-create-homedir-if-needed ended up being duplicated across {chaiwala,apertis}-customizations and this duplication trickled down to infrastructure/apertis-image-recipes>.

To address that, sync the copy here so we can later drop the one in infrastructure/apertis-image-recipes> by installing chaiwala-user-session-wayland and then masking out the actual chaiwala-user@seat0-1000.service unit.

On the other hand, apertis-customizations@7975b714 may suggest that we should not pursue this road and we should instead put everything in the image recipes, even if that makes updates (on the SDK) more difficult.