[sddm-theme] Handle passwordless accounts
As described here https://github.com/sddm/sddm/issues/751#issuecomment-847347450
SDDM provides the
needsPassword property, which can be used to hide the password prompt for passwordless accounts.
This merge request provides a basic implementation for the breeze SDDM theme.
The addition was tested at tag v220.127.116.11 on Ubuntu 20.04.2 LTS (Focal Fossa).
It has been merged into
work/tpecar/sddm-theme-passwordless which has been based on current master (2f4b27fc).