continue uploading media after sending post (#4662)

regression from #4599

https://pug.ninja/@motoridersd/113102603349423738

The problem is, `MediaUploader` is no longer a singleton, so the state
is not correctly shared between `ComposeActivity` and
`SendStatusService.` But it can't be a singleton, since `MediaUploadApi`
(injected into `MediaUploader`) needs to be recreated on account change.
Let's share the state in the companion object instead.

app/src/main/java/com/keylesspalace/tusky/components/compose/MediaUploader.kt

@@ -97,9 +97,11 @@ class MediaUploader @Inject constructor(
     private val mediaUploadApi: MediaUploadApi
 ) {
 
-    private val uploads = mutableMapOf<Int, UploadData>()
-
-    private var mostRecentId: Int = 0
+    private companion object {
+        private const val TAG = "MediaUploader"
+        private val uploads = mutableMapOf<Int, UploadData>()
+        private var mostRecentId: Int = 0
+    }
 
     fun getNewLocalMediaId(): Int {
         return mostRecentId++
@@ -326,8 +328,4 @@ class MediaUploader @Inject constructor(
         return media.type == QueuedMedia.Type.IMAGE &&
             (media.mediaSize > instanceInfo.imageSizeLimit || getImageSquarePixels(context.contentResolver, media.uri) > instanceInfo.imageMatrixLimit)
     }
-
-    private companion object {
-        private const val TAG = "MediaUploader"
-    }
 }