add performance upgrades to media picker

- Use jpeg instead of png data when processing a UIImage.
- Make processing of media occur after user confirms upload selection when possible for better responsiveness.
- Reduce redundant data fetching.

Lightning-address: kernelkind@getalby.com
Signed-off-by: kernelkind <kernelkind@gmail.com>
Link: 20240228033235.66935-2-kernelkind@gmail.com
Signed-off-by: William Casarin <jb55@jb55.com>

damus/Models/ImageUploadModel.swift

@@ -8,6 +8,13 @@
 import Foundation
 import UIKit
 
+enum PreUploadedMedia {
+    case uiimage(UIImage)
+    case processed_image(URL)
+    case unprocessed_image(URL)
+    case processed_video(URL)
+    case unprocessed_video(URL)
+}
 
 enum MediaUpload {
     case image(URL)