The initialDirectory parameter of getDirectoryPath does not support POSIX-style paths

[twinkles-twinstar]

Describe the bug
When using the getDirectoryPath API, if the initialDirectory parameter is set to a POSIX-style path (/path/to/file), the app will crash. When a Windows-style path is set (\path\to\file), the app will run normally.
However, both pickFiles and saveFile APIs support the use of POSIX-style paths, only getDirectoryPath does not allow it.
On Windows platforms, should file_picker internally convert initialDirectory to Windows-style?

Platform

• Android
• iOS
• Web
• Desktop

Platform OS version
Windows 11 23H2

How are you picking?

FilePicker.platform.pickFiles(initialDirectory: 'C:/'); // ok
FilePicker.platform.getDirectoryPath(initialDirectory: 'C:/'); // crash
FilePicker.platform.getDirectoryPath(initialDirectory: 'C:\\'); // ok

Flutter Version details
v3.19.6, all ok.

[github-actions]

This issue is stale because it has been open for 7 days with no activity.