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>

libraries/matrix/test/src/main/kotlin/io/element/android/libraries/matrix/test/notification/NotificationData.kt

@@ -34,6 +34,7 @@ fun aNotificationData(
         roomAvatarUrl = null,
         roomDisplayName = null,
         isDirect = false,
+        isDm = false,
         isEncrypted = false,
         isNoisy = false,
         timestamp = 0L,

libraries/matrix/test/src/main/kotlin/io/element/android/libraries/matrix/test/room/FakeMatrixRoom.kt

@@ -80,7 +80,6 @@ class FakeMatrixRoom(
     override val isPublic: Boolean = true,
     override val isSpace: Boolean = false,
     override val isDirect: Boolean = false,
-    override val isOneToOne: Boolean = false,
     override val joinedMemberCount: Long = 123L,
     override val activeMemberCount: Long = 234L,
     val notificationSettingsService: NotificationSettingsService = FakeNotificationSettingsService(),