delta-computer: stop explicitly taking file handle The revlog has all the logic for opening and caching such handles, so no need to duplicate it here. In addition, this let the revlog handle that logic by itself which is better.

censors: simply use `revlog.reading` to keep things open dring rewrite We have a dedicated context now, we can simply use it. In practice, we cannot "simply" use it, as `finddeltainfo` still requires the file pointer to be passed explicitly. We will keep the old context manager open for a small bit until we get rid of it in a future changeset.

stream-clone: use `revlog.reading` in `revlog.get_streams` We can get the same result while using more standard method, so we do.