Feature or enhancement

In #101324, @eryksun pointed out that we could also optimize os.path.isjunction(), and would like see the same ~25% speedup as for isdir, isfile and islink:

Maybe also add nt._isjunction() for the new ntpath.isjunction() test in 3.12. It's like islink(), except it checks for the tag IO_REPARSE_TAG_MOUNT_POINT. In the LSTAT fallback, it would check st.st_reparse_tag == IO_REPARSE_TAG_MOUNT_POINT.

It's not critical to support this since we don't have use cases for it yet in the standard library. Currently DirEntry.is_junction() is used by shutil.rmtree(), but ntpath.isjunction() is only used by pathlib.Path.is_junction().