Reply rendering (#861)

* Cleanup how we use message timeline items in preparation for rich reply rendering

* Expose reply details up to the UI level

* Render replies in the timeline (textual for now). Remove now unused AttributedStringBuilderComponent isReply flag.

* Move reply detail loading to when the item appears instead of when it's created.

* Fix unit tests

* Fetch event details also when the reply details are in the error state

* Tweaks following code review

* Localise emote bodies

* Fix replies not loading sometimes, use the current event identifier instead of the one being replied to

UnitTests/Sources/RoomScreenViewModelTests.swift

@@ -155,11 +155,11 @@ class RoomScreenViewModelTests: XCTestCase {
 private extension TextRoomTimelineItem {
     init(text: String, sender: String, addReactions: Bool = false) {
         self.init(id: UUID().uuidString,
-                  body: text,
                   timestamp: "10:47 am",
                   isOutgoing: sender == "bob",
                   isEditable: sender == "bob",
                   sender: .init(id: "@\(sender):server.com", displayName: sender),
+                  content: .init(body: text),
                   properties: RoomTimelineItemProperties(reactions: addReactions ? [
                       AggregatedReaction(key: "🦄", count: 1, isHighlighted: false)
                   ] : []))