sftp support sudo login like winscp to copy files

sftp support sudo login like winscp to copy files
reference this
https://winscp.net/eng/docs/faq_su

right now it can only support login user permission copy.

for most server , you need to do `sudo su ` to access other folder

winscp give a example how to do this

winscp可以拷贝 任意目录， 实现原理如上面链接。
希望有同样的功能

Start by reviewing the linked WinSCP FAQ and the existing SFTP login and copy flow; the issue names no repository files, tests, or entry points. Done means users can authenticate with elevated access and copy files from directories unavailable to the login user, with the behavior covered by an appropriate test.

Written by the indexing model from the issue text.