Use sftp RENAME instead of copy and delete in case of moving a file

Hello,
I use fsspec to have a single api to work with multiple different storage backend.
I ran into some issues with the sftp implementation because the move method is used and fails with the error : asyncssh.misc.ChannelOpenError: Session request failed trying to do a cp command here https://github.com/fsspec/sshfs/blob/main/sshfs/spec.py#L162

From what I understand the cp command is not always (rarely ?) possible on sftp protocol and the posix_rename is not always supported either.
Would it be possible to replace this to copy and then remove the file by a sftp rename ?
In my case, that did fix the issue and this is the approach used for example in the fs.sshfs implementation. (https://github.com/althonos/fs.sshfs/blob/master/fs/sshfs/sshfs.py#L279)
And it seems quite easy since the rename is already implemented in asyncssh.
I could do a PR about it is an acceptable change.

Start in sshfs/spec.py at the move implementation linked in the issue, and review how asyncssh exposes rename. Verify the move path uses SFTP rename rather than the failing cp command, then run the existing test suite or add coverage for moving a file and confirm the operation succeeds without the session request error.