Get a trigger of addSnapshotListener() or listen to changes in specific properties

## What feature would you like to see?

I would like to 1) receive snapshots only if certain properties are updated (i.e. do not receive snapshots if some other properties are updated) or 2) find a source which triggered the snapshot listener, so that I can check properties.
It can be done by comparing the existing object with a newly received, but I would like to avoid it as it will result in spaghetti code.

## How would you use it?

1) For properties to exclude
FireStoreCollectionOrDocument
.addSnapshotListener(
new String[] {"prop1", "prop2"},
(doc, ex) -> { ... });

2) For checking the listener trigger
FireStoreCollectionOrDocument
.addSnapshotListener((doc, ex, metaData) -> {
String a = metaData.getTriggerProperty();
// or String[] b = metaData.getTriggerProperties();
...
})

Beginne mit der Überprüfung der bestehenden addSnapshotListener()-API und des im Issue beschriebenen Firestore-Listener-Verhaltens. Vergleiche die beiden vorgeschlagenen Ansätze – das Filtern nach Eigenschaften oder das Offenlegen der Trigger-Eigenschaften – und lege fest, welches Verhalten, welche API-Struktur und welche Abschlusskriterien das Projekt akzeptieren würde.

Vom Indexierungsmodell aus dem Issue-Text verfasst.