Remove delivered notifications for rooms that have meantime become fully read and have messages newer than what's delivered

- this is a best effort solution to cleanup outdated notifications when using multiple clients and reading them elsewhere

ElementX/Sources/Services/Room/RoomSummary/RoomSummary.swift

@@ -40,6 +40,7 @@ struct RoomSummary {
     let avatarURL: URL?
     let heroes: [UserProfileProxy]
     let lastMessage: AttributedString?
+    let lastMessageDate: Date?
     let lastMessageFormattedTimestamp: String?
     let unreadMessagesCount: UInt
     let unreadMentionsCount: UInt
@@ -95,6 +96,7 @@ extension RoomSummary {
         avatarURL = nil
         heroes = []
         lastMessage = AttributedString(string)
+        lastMessageDate = .now
         lastMessageFormattedTimestamp = "Now"
         unreadMessagesCount = hasUnreadMessages ? 1 : 0
         unreadMentionsCount = hasUnreadMentions ? 1 : 0