Support copying files from Explorer to system clipboard for pasting outside VS Code

Title: Support copying files from Explorer to system clipboard for pasting outside VS Code

**Description**

When copying a file in the VS Code Explorer, it is currently impossible to paste the file directly to the operating system (e.g., Windows File Explorer, or the desktop). The copied file can only be successfully pasted between different VS Code windows.

This is a very common and expected capability in almost all development tools and file managers. Users frequently need to copy files from their project and paste them elsewhere on their computer, such as sending files via chat apps, attaching files to emails, or organizing files in the OS file manager. It would be great if VS Code could support this.

**Steps to Reproduce**

1. Open a folder in VS Code
2. Right-click a file in the Explorer and select "Copy" (or press `Ctrl+C` / `Cmd+C`)
3. Switch to the OS file manager (e.g., Windows File Explorer)
4. Attempt to paste (`Ctrl+V` / `Cmd+V`)

**Expected Behavior**

The copied file should be pasted to the target location in the OS file manager, just like copying a file in the native file manager.

**Actual Behavior**

Nothing is pasted. The file can only be pasted within VS Code itself (e.g., in another VS Code window).

**Additional Context**

This feature is standard in many other IDEs and editors (e.g., JetBrains IDEs allow copying files to the system clipboard and pasting them into the OS). Supporting this would significantly improve workflow efficiency when transferring files between VS Code and other applications.