Move RoomSummaryConstants to MatrixConfiguration

Clients of the SDK should be able to decide what can be considered as a previewable events (used for room list for instance).

Documentation must mention that changing this value may lead to unexpected behavior.

Currently this is hard-coded here: https://github.com/vector-im/element-android/blob/main/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/session/room/summary/RoomSummaryConstants.kt#L26

The configuration can have this default value, or if null use this default value, not sure what is the best approach here.