Add support for sending media within threads.

This patch add the `threadRootEventID` as a parameter to media sending functions and forwards the timeline thread root between various application states to the place where its needed.
The 2 missing items are Locations and Polls which currently don't have any support on the Rust side for being sent within threads. That will come in a separate PR.

ElementX/Sources/Screens/MediaUploadPreviewScreen/MediaUploadPreviewScreenCoordinator.swift

@@ -14,6 +14,7 @@ struct MediaUploadPreviewScreenCoordinatorParameters {
     let mediaUploadingPreprocessor: MediaUploadingPreprocessor
     let title: String?
     let url: URL
+    let threadRootEventID: String?
     let shouldShowCaptionWarning: Bool
 }
 
@@ -36,6 +37,7 @@ final class MediaUploadPreviewScreenCoordinator: CoordinatorProtocol {
                                                       mediaUploadingPreprocessor: parameters.mediaUploadingPreprocessor,
                                                       title: parameters.title,
                                                       url: parameters.url,
+                                                      threadRootEventID: parameters.threadRootEventID,
                                                       shouldShowCaptionWarning: parameters.shouldShowCaptionWarning)
     }