Implement DiffUtil for OCFileListAdapter

[DiffUtil](https://developer.android.com/reference/androidx/recyclerview/widget/DiffUtil) is a utility class that calculates the difference between two lists and outputs a list of update operations that converts the first list into the second one.

Using notifyDataSetChanged() in RecyclerView doesn’t let it track the exact changes. As a result, all visible views are needlessly rebuilt, which is inefficient and time-consuming.

By using DiffUtil, we can compare the old and new lists more efficiently. This way, only the specific items that have changed are updated, avoiding the full rebuild.