Add Device RSSIChanged and generic PropertyChanged events

[Kinchul]

Details

Add RSSIChanged and generic PropertyChanged events to Device

Device.OnPropertyChanges only surfaced Connected and ServicesResolved; all other Device1 property changes were received by the existing property watcher and discarded.

This adds two events, reusing that same watcher (no extra D-Bus subscriptions):

• RSSIChanged (EventHandler<short>) — typed event carrying the new RSSI in dBm, matching the existing typed-event style. Lets consumers track signal strength across advertisements without polling or re-scanning.
• PropertyChanged (EventHandler<PropertyChanges>) — generic passthrough of the raw changes for every property, so properties without a dedicated event (e.g. ManufacturerData, TxPower) are reachable without forking the library.

Note

Changes covered by a typed event (Connected, ServicesResolved, RSSI) are also delivered on PropertyChanged; this is documented as intentional on the event.

[Kinchul]

Pushed one follow-up fix found while running this on hardware:

Exceptions escaping the property-changed handler. OnPropertyChanges runs on the D-Bus
receive loop, and this PR gives consumers two new places to subscribe. A subscriber throwing
there propagates into Tmds.DBus, which treats it as a fatal receive error, disconnects, and
discards every signal handler on the connection — method calls keep working while all events
go silent. The handler now contains consumer exceptions and logs them.