Add post editing capability (#2828)

* Add post editing capability

* Don't try to reprocess already uploaded attachments.
Fixes editing posts with existing media

* Don't mark post edits as modified until editing occurs

* Disable UI for things that can't be edited when editing a post

* Finally convert SFragment to kotlin

* Use api endpoint for fetching status source for editing

* Apply review feedback

app/src/main/java/com/keylesspalace/tusky/db/DraftEntity.kt

@@ -42,6 +42,7 @@ data class DraftEntity(
     val failedToSend: Boolean,
     val scheduledAt: String?,
     val language: String?,
+    val statusId: String?,
 )
 
 /**