MM-18522: Include edited posts in compliance export. (#12197)

* MM-18522: Export all post edits in compliance exports.

* MM-18522: Changes ordering of export query post results.

model/message_export.go

@@ -20,6 +20,7 @@ type MessageExport struct {
 
 	PostId         *string
 	PostCreateAt   *int64
+	PostUpdateAt   *int64
 	PostMessage    *string
 	PostType       *string
 	PostRootId     *string