replace file transfer backend with SSH.NET

Description

The file transfer functionality uses very old libraries that haven't been updated in ages and are likely very insecure at this point. Replace them with SSH.NET.

This will also lay down the basic framework for SSH sessions to be created without PuTTY.

Environment

None

Status

Assignee

Sean K

Reporter

Sean K

Labels

None

Fix versions

Priority

Blocker
Configure