[nemo-qml-plugin-systemsettings] Refactor location settings. Contributes to JB#47257
Adjusted for better maintainability.
- Api addition: pendingAgreements tells which location services are missing acceptance on currently set location mode
- Some code moved around for grouping both deprecated parts and location services together
- Yandex locator enabled setting removed, was copy-paste detail from mls which has both offline and online variants.
- agps_providers on settings file didn't appear used by anything. Removed.
- Removed writing deprecated keys, only need to read them (if even that).
- Simplified lots of things
Was considering blowing up the api more, but ended up doing this now first by mostly api-compatible way. UI side needs to know anyway the specific agreements and behavioral details. Further adjustments now easier as there aren't anymore tens of lines of logical operators on different things.