SFTP is unable to fetch files with backslashes in their name

Prerequisites

• Write a descriptive title.
• Make sure you are able to repro it on the latest version
• Search the existing issues.

Steps to reproduce

1. On a (Unix) remote, create a file named foo\bar with: touch 'foo\bar'
2. From Windows: sftp <user>@<remote>
3. get 'foo\\bar' 'foo-bar'

Expected behavior

`Fetching /home/<user>/foo\bar to foo-bar`

Actual behavior

`File "/home/<user>/foo//bar" not found`.

Error details

No response

Environment data

Name                           Value
----                           -----
PSVersion                      7.2.7
PSEdition                      Core
GitCommitId                    7.2.7
OS                             Microsoft Windows 10.0.22621
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

Version

PowerShell 7.2.7

Visuals

No response

Start by reproducing the Windows PowerShell 7.2.7 command against a Unix remote, using a filename containing a backslash as described. Trace the SFTP path handling and verify that the backslash remains part of the remote filename rather than becoming a separator; done when the fetch succeeds with the reported command.