Stabilize Windows FileTypeExt with is_symlink_dir and is_symlink_file

These calls allow detecting whether a symlink is a file or a directory,
a distinction Windows maintains, and one important to software that
wants to do further operations on the symlink (e.g. removing it).

Author: joshtriplett

library/std/src/os/windows/fs.rs

@@ -502,17 +502,17 @@ impl MetadataExt for Metadata {
 /// Windows-specific extensions to [`fs::FileType`].
 ///
 /// On Windows, a symbolic link knows whether it is a file or directory.
-#[unstable(feature = "windows_file_type_ext", issue = "none")]
+#[stable(feature = "windows_file_type_ext", since = "1.64.0")]
 pub trait FileTypeExt {
     /// Returns `true` if this file type is a symbolic link that is also a directory.
-    #[unstable(feature = "windows_file_type_ext", issue = "none")]
+    #[stable(feature = "windows_file_type_ext", since = "1.64.0")]
     fn is_symlink_dir(&self) -> bool;
     /// Returns `true` if this file type is a symbolic link that is also a file.
-    #[unstable(feature = "windows_file_type_ext", issue = "none")]
+    #[stable(feature = "windows_file_type_ext", since = "1.64.0")]
     fn is_symlink_file(&self) -> bool;
 }
 
-#[unstable(feature = "windows_file_type_ext", issue = "none")]
+#[stable(feature = "windows_file_type_ext", since = "1.64.0")]
 impl FileTypeExt for fs::FileType {
     fn is_symlink_dir(&self) -> bool {
         self.as_inner().is_symlink_dir()