GH-73991: Make pathlib.Path.delete() private. (#123315)

Per feedback from Paul Moore on GH-123158, it's better to defer making
`Path.delete()` public than ship it with under-designed error handling
capabilities.

We leave a remnant `_delete()` method, which is used by `move()`. Any
functionality not needed by `move()` is deleted.

Lib/pathlib/_local.py

@@ -824,34 +824,7 @@ class Path(PathBase, PurePath):
         """
         os.rmdir(self)
 
-    def delete(self, ignore_errors=False, on_error=None):
-        """
-        Delete this file or directory (including all sub-directories).
-
-        If *ignore_errors* is true, exceptions raised from scanning the
-        filesystem and removing files and directories are ignored. Otherwise,
-        if *on_error* is set, it will be called to handle the error. If
-        neither *ignore_errors* nor *on_error* are set, exceptions are
-        propagated to the caller.
-        """
-        if self.is_dir(follow_symlinks=False):
-            onexc = None
-            if on_error:
-                def onexc(func, filename, err):
-                    err.filename = filename
-                    on_error(err)
-            shutil.rmtree(str(self), ignore_errors, onexc=onexc)
-        else:
-            try:
-                self.unlink()
-            except OSError as err:
-                if not ignore_errors:
-                    if on_error:
-                        on_error(err)
-                    else:
-                        raise
-
-    delete.avoids_symlink_attacks = shutil.rmtree.avoids_symlink_attacks
+    _rmtree = shutil.rmtree
 
     def rename(self, target):
         """