oniro-linux: Add sftp-server package

Modern ssh clients use SFTP protocol and refuse to connect using SCP protocol (dropbear uses) by default. Adding sftp-server to allow sftp connections in Oniro. This requires workaround for [Yocto #14858] to be applied for every Oniro images, not only extra-tests.

Fixes: #774 (closed)

Signed-off-by: Pavel Zhukov pavel.zhukov@huawei.com