gh-106739: Add rtype_cache to warnings.warn message when leaked objects found (#106740)

Adding the `rtype_cache` to the `warnings.warn` message improves the
previous, somewhat vague message from

```
/Users/username/cpython/Lib/multiprocessing/resource_tracker.py:224: UserWarning: resource_tracker: There appear to be 6 leaked semaphore objects to clean up at shutdown
```

to

```
/Users/username/cpython/Lib/multiprocessing/resource_tracker.py:224: UserWarning: resource_tracker: There appear to be 6 leaked semaphore objects to clean up at shutdown: {'/mp-yor5cvj8', '/mp-10jx8eqr', '/mp-eobsx9tt', '/mp-0lml23vl', '/mp-9dgtsa_m', '/mp-frntyv4s'}
```

---------

Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>

Author: shailshouryya

Lib/multiprocessing/resource_tracker.py

@@ -221,9 +221,10 @@ def main(fd):
         for rtype, rtype_cache in cache.items():
             if rtype_cache:
                 try:
-                    warnings.warn('resource_tracker: There appear to be %d '
-                                  'leaked %s objects to clean up at shutdown' %
-                                  (len(rtype_cache), rtype))
+                    warnings.warn(
+                        f'resource_tracker: There appear to be {len(rtype_cache)} '
+                        f'leaked {rtype} objects to clean up at shutdown: {rtype_cache}'
+                    )
                 except Exception:
                     pass
             for name in rtype_cache:

Misc/NEWS.d/next/Library/2023-07-20-06-00-35.gh-issue-106739.W1hygr.rst

@@ -0,0 +1 @@
+Add the ``rtype_cache`` to the warning message (as an addition to the type of leaked objects and the number of leaked objects already included in the message) to make debugging leaked objects easier when the multiprocessing resource tracker process finds leaked objects at shutdown. This helps more quickly identify what was leaked and/or why the leaked object was not properly cleaned up.