[testing] Add test owner labels for some distributed tests (#163174)

I am trying to give some test files better owner labels than `module: unknown`.  I am not sure them, but they seem pretty reasonable

Pull Request resolved: https://github.com/pytorch/pytorch/pull/163174
Approved by: https://github.com/ezyang

test/distributed/_tools/test_fake_collectives.py

@@ -1,4 +1,4 @@
-# Owner(s): ["module: unknown"]
+# Owner(s): ["oncall: distributed"]
 import unittest
 
 import torch

test/distributed/_tools/test_fsdp2_mem_tracker.py

@@ -1,4 +1,4 @@
-# Owner(s): ["module: unknown"]
+# Owner(s): ["module: fsdp"]
 import functools
 import gc
 from typing import Union

test/distributed/_tools/test_mem_tracker.py

@@ -1,4 +1,4 @@
-# Owner(s): ["module: unknown"]
+# Owner(s): ["oncall: distributed"]
 import gc
 import unittest
 

test/distributed/_tools/test_mod_tracker.py

@@ -1,4 +1,4 @@
-# Owner(s): ["module: unknown"]
+# Owner(s): ["oncall: distributed"]
 
 from copy import copy
 

test/distributed/_tools/test_runtime_estimator.py

@@ -1,4 +1,4 @@
-# Owner(s): ["module: unknown"]
+# Owner(s): ["oncall: distributed"]
 import unittest
 from dataclasses import dataclass
 from typing import Any, Callable, cast, Union

test/distributed/_tools/test_sac_estimator.py

@@ -1,4 +1,4 @@
-# Owner(s): ["module: unknown"]
+# Owner(s): ["oncall: distributed"]
 import unittest
 
 import torch

test/distributed/_tools/test_sac_ilp.py

@@ -1,4 +1,4 @@
-# Owner(s): ["module: unknown"]
+# Owner(s): ["oncall: distributed"]
 import copy
 import unittest