kcm: Show "Never" when Autolock is false

Summary

Show "Never" for automatic screen locking when Autolock=false, regardless of the Timeout value.

Problem

Autolock and Timeout are configured independently. It is therefore possible to have a configuration where Autolock=false while Timeout is unset or has a non-zero value, such as 5.

The KCM currently selects the displayed option based only on Timeout. As a result, with Autolock=false and Timeout=5, the user sees "5 minutes" even though automatic screen locking is disabled.

This creates two visible inconsistencies:

1. kscreenlocker starts the timer only when both autolock() is enabled and timeout() > 0: ksldapp.cpp. Therefore, the screen does not lock after the five minutes displayed by the KCM.
2. On the same KCM page, the availability of the password delay field depends on kcm.settings.autolock: extraEnabledConditions: kcm.settings.autolock. As a result, the KCM displays "5 minutes" while also disabling a field that should be available when automatic screen locking is enabled.

Regression

The KCM previously handled Autolock=false explicitly and returned the index of the "Never" option in that case: timeoutOptionsCurrentIndexForSavedValue() before the change.

This check disappeared on April 28, 2024 in commit ae72db155bdee50fa6a9a04ee925d1b5cb9c41bc, merged through MR !217, "kcm: Factor out ComboBoxWithCustomValue for later reuse". After the refactoring, configuredValue was based only on Timeout, and the previous branch for disabled Autolock was not carried over.