Fix DM logic to always pick a more reliable DM room

Fixes https://github.com/vector-im/element-web/issues/15605

src/utils/membership.ts

@@ -78,6 +78,11 @@ export function getEffectiveMembership(membership: string): EffectiveMembership
     }
 }
 
+export function isJoinedOrNearlyJoined(membership: string): boolean {
+    const effective = getEffectiveMembership(membership);
+    return effective === EffectiveMembership.Join || effective === EffectiveMembership.Invite;
+}
+
 export async function leaveRoomBehaviour(roomId: string) {
     let leavingAllVersions = true;
     const history = await MatrixClientPeg.get().getRoomUpgradeHistory(roomId);