GH-115060: Speed up `pathlib.Path.glob()` by omitting initial `stat()` (#117831)

Since 6258844c, paths that might not exist can be fed into pathlib's
globbing implementation, which will call `os.scandir()` / `os.lstat()` only
when strictly necessary. This allows us to drop an initial `self.is_dir()`
call, which saves a `stat()`.

Co-authored-by: Shantanu <12621235+hauntsaninja@users.noreply.github.com>