Add setting for customizable delimiter for file drag-and-drop

[Vallabh-1504]

Summary of the Pull Request

This PR introduces a new profile setting, dragDropDelimiter, which allows users to configure the string separator used when dragging and dropping multiple files into the terminal. The default behavior remains a single space (" ") for backward compatibility.

References and Relevant Issues

• Closes Configurable delimiter when drag-and-drop multiple files #19565

Detailed Description of the Pull Request / Additional comments

Implementation Details:

• Settings: Added DragDropDelimiter to MTSMSettings.h and Profile.idl.
• Control: Wired the setting through ControlProperties.h so the terminal logic can see it.
• Logic: Updated TermControl::OnDrop to use the new delimiter when joining paths.
• UI: Added the text box in the Advanced Settings page and updated the ViewModel.

Demo

demo1.mp4

Validation Steps Performed

• Manual Verification:
  • Verified default behavior (space separator) works as before.
  • Configured dragDropDelimiter to ", ", ";", and custom strings in settings.json and from settings UI.
  • Confirmed dropped files are joined correctly.
• Build: Validated that the solution builds cleanly.

Notes for Reviewers

1. Delimiter Length: Currently, there is no limit on the maximum length of the delimiter string. Let me know if this should be changed.
2. Localization: I changed only Resources/en-US file.
3. ViewModel: In ProfileViewModel.cpp, I added the else if block for the new setting, but left it empty because no other UI logic currently depends on it.

PR Checklist

• Closes Configurable delimiter when drag-and-drop multiple files #19565
• Tests added/passed
• Documentation updated
• Schema updated (if necessary)