Unescape mount point paths read from /proc/mounts

This makes mounts that have symbols " \t\n\\" actually appear in the
volumes list in the ManagedFileChooser dialog.

src/Avalonia.FreeDesktop/LinuxMountedVolumeInfoListener.cs

@@ -36,6 +36,11 @@ namespace Avalonia.FreeDesktop
 
         private string GetSymlinkTarget(string x) => Path.GetFullPath(Path.Combine(DevByLabelDir, NativeMethods.ReadLink(x)));
 
+        private string UnescapeString(string input, string regexText, int escapeBase) =>
+            new Regex(regexText).Replace(input, m => Convert.ToChar(Convert.ToByte(m.Groups[1].Value, escapeBase)).ToString());
+
+        private string UnescapePathFromProcMounts(string input) => UnescapeString(input, @"\\(\d{3})", 8);
+
         private void Poll(long _)
         {
             var fProcPartitions = File.ReadAllLines(ProcPartitionsDir)
@@ -47,7 +52,7 @@ namespace Avalonia.FreeDesktop
 
             var fProcMounts = File.ReadAllLines(ProcMountsDir)
                                   .Select(x => x.Split(' '))
-                                  .Select(x => (x[0], x[1]))
+                                  .Select(x => (x[0], UnescapePathFromProcMounts(x[1])))
                                   .Where(x => !x.Item2.StartsWith("/snap/", StringComparison.InvariantCultureIgnoreCase));
 
             var labelDirEnum = Directory.Exists(DevByLabelDir) ?