positioning/ohos: deduplicate satellites

A single satelliteStatusChange update may report the same
(satelliteSystem, satelliteIdentifier) pair more than once, e.g. when a
satellite is tracked on multiple carrier frequencies. QGeoSatelliteInfo
cannot represent the carrier frequency, so these entries share the same
identity, and consumers such as the satelliteinfo example's
SatelliteModel assume satellitesInView lists each satellite only once.
Emitting duplicates there leads to an out-of-range list access.

Deduplicate satellitesInView and satellitesInUse on (system, id),
keeping the first occurrence, mirroring the Android backend in
58bbf8fa5fdeb1c19d71cdab8830b9cf55672a5e ("Android: avoid duplicated
entries when reporting satellite info").

Pick-to: 6.12
Change-Id: Ic0ca8196489b40c41fb8cc7f0b59c09c311caba5
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>