Unify the way we decide whether a room is a DM or a group room (#3100)

* Add centralised 'room is DM' check

Also add extension functions for `MatrixRoom` and `MatrixRoomInfo`.

* Use the centralised method and extension functions through the app, including:

- Room list.
- Room details screen.
- Invites.
- Notifications.

Replace most `isDirect` usages with `isDm`.

* Update screenshots

---------

Co-authored-by: ElementBot <benoitm+elementbot@element.io>

features/invite/api/src/main/kotlin/io/element/android/features/invite/api/response/AcceptDeclineInviteStateProvider.kt

@@ -27,13 +27,13 @@ open class AcceptDeclineInviteStateProvider : PreviewParameterProvider<AcceptDec
             anAcceptDeclineInviteState(),
             anAcceptDeclineInviteState(
                 invite = Optional.of(
-                    InviteData(RoomId("!room:matrix.org"), isDirect = true, roomName = "Alice"),
+                    InviteData(RoomId("!room:matrix.org"), isDm = true, roomName = "Alice"),
                 ),
                 declineAction = AsyncAction.Confirming,
             ),
             anAcceptDeclineInviteState(
                 invite = Optional.of(
-                    InviteData(RoomId("!room:matrix.org"), isDirect = false, roomName = "Some room"),
+                    InviteData(RoomId("!room:matrix.org"), isDm = false, roomName = "Some room"),
                 ),
                 declineAction = AsyncAction.Confirming,
             ),

features/invite/api/src/main/kotlin/io/element/android/features/invite/api/response/InviteData.kt

@@ -21,5 +21,5 @@ import io.element.android.libraries.matrix.api.core.RoomId
 data class InviteData(
     val roomId: RoomId,
     val roomName: String,
-    val isDirect: Boolean,
+    val isDm: Boolean,
 )