Add SFTP remote file transfer functionality

[raohj1987]

Description

The current SSH file transfer function is not very user-friendly. Among the remote file transfer tools I have used, Xshell provides a relatively good experience. Therefore, referring to the features of Xshell, similar functionality has been added to mRemoteNG.

Motivation and Context

The current SSH file transfer function is not very user-friendly. Among the remote file transfer tools I have used, Xshell provides a relatively good experience. Therefore, referring to the features of Xshell, similar functionality has been added to mRemoteNG.

How Has This Been Tested?

This modification basically does not change the existing functionality; it just adds code to increase the corresponding functionality. I have conducted thorough testing on my own computer. The key points of the testing include the following:
1、When a terminal is currently open, clicking Tools -> SFTP File Manager will reuse the current connection.
2、This feature supports uploading and downloading files and folders. It also has a corresponding progress bar display.

Screenshots (if appropriate):

Types of changes

• [] Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Changed feature (non-breaking change which changes functionality)
• Changed feature (breaking change which changes functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Updated translation

Checklist:

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• All Tests within VisualStudio are passing
• This pull request does not target the master branch.
• I have updated the changelog file accordingly, if necessary.
• I have updated the documentation accordingly, if necessary.

[sonarqubecloud]

Quality Gate failed

Failed conditions
5.1% Duplication on New Code (required ≤ 3%)

See analysis details on SonarQube Cloud