Add KDED module for adjusting the system time zone based on location

We don't need accurate location data, so it just talks to the KDE geoip endpoint directly and adjusts the timezone accordingly.

It does that only on a network with full connectivity (ie. not behind a portal), that is not metered and not connected to a VPN (to avoid using the VPN gateway's timezone inadvertendly).

It only does it max every 24 hours, unless the user connected to a new connection to ensure prompt update when arriving at a new location.

The module is off-by-default to not do unsolicited network requests and can be enabled from datetime settings.

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@vkrause @sitter @leinir

Fixes people running around at Akademy with the wrong time on their laptops.

KCM plasma-desktop!2401

or load the module manually:

$ qdbus org.kde.kded6 /kded org.kde.kded6.loadModule geotimezoned

or enable autoloading and restart KDED:

$ qdbus org.kde.kded6 /kded org.kde.kded6.setModuleAutoloading geotimezoned true

There’s a logging category org.kde.plasma.geotimezoned you can enable for more verbose output.