installer: Limit listbox height.

installer: Limit listbox height.

Fixes: <https://issues.guix.gnu.org/44428>.

* gnu/installer/newt.scm (init): Print screen size.
* gnu/installer/newt/page.scm (default-listbox-height): New variable.
(run-listbox-selection-page): Use it.
* gnu/installer/newt/wifi.scm (wifi-listbox-height): Ditto.
* gnu/installer/newt/network.scm (run-technology-page): Set the maximum
listbox height to 5.
* gnu/installer/newt/ethernet.scm (run-ethernet-page): Ditto.
* gnu/installer/newt/final.scm (run-config-display-page): Change listbox
height.
* gnu/installer/newt/partition.scm (run-disk-page): Ditto.
* gnu/installer/newt/welcome.scm (display-logo?): New procedure.
(run-menu-page): Use it.
* gnu/installer/steps.scm (%configuration-file-width): Remove it.