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

ElementX/Sources/Services/Timeline/TimelineItems/EventBasedTimelineItemProtocol.swift

@@ -18,7 +18,6 @@ import Foundation
 import UIKit
 
 protocol EventBasedTimelineItemProtocol: RoomTimelineItemProtocol, CustomStringConvertible {
-    var body: String { get }
     var timestamp: String { get }
     var isOutgoing: Bool { get }
     var isEditable: Bool { get }