fix(bootloader-interface): show the menu for LoaderConfigTimeoutOneShot

LoaderConfigTimeoutOneShot asks the boot loader to show the menu on the
next boot, and a value of 0 means the menu waits for the user. Sprout
treated it like LoaderConfigTimeout, so 0 hid the menu, the opposite of
what systemctl reboot --boot-loader-menu=0 asks for, and other values
only changed the timeout without forcing the menu.

Force the menu when the one-shot timeout is set, waiting for the user
when it is 0.

crates/boot/src/main.rs

@@ -302,6 +302,12 @@ fn run() -> Result<()> {
             wait_for_user = true;
         }
 
+        BootloaderInterfaceTimeout::MenuForceTimeout(timeout) => {
+            // Force the boot menu with the specified timeout.
+            force_boot_menu = true;
+            menu_timeout = timeout;
+        }
+
         BootloaderInterfaceTimeout::MenuHidden | BootloaderInterfaceTimeout::MenuDisabled => {
             // Hide the boot menu by setting the timeout to zero.
             menu_timeout = 0;