Keep the {driver} placeholder working and support older
power-profiles-daemon versions that only expose a single Driver DBus
property, while still reading the new CpuDriver/PlatformDriver fields.
- Read the legacy Driver property and fall back to it when CpuDriver or
PlatformDriver are missing (older daemon).
- Derive {driver} from CpuDriver when the daemon no longer exposes
Driver (recent daemon), so existing configs using {driver} keep
working.
- Align the default tooltip-format in the constructor with the
documented default.
Alex
fe0e1c139b