Improve TORCH_LOGS settings error msg (pytorch#97264)

Lists registered loggable entities if an invalid settings string is passed via TORCH_LOGS
[before](https://gist.github.com/mlazos/91fcbc3d577f874bcb3daea44f8b41f2)
[after](https://gist.github.com/mlazos/815ea9e76aca665602228f960e0eb0d6)
Pull Request resolved: pytorch#97264
Approved by: https://github.com/ezyang, https://github.com/jansel

torch/_logging/_internal.py

@@ -253,15 +253,26 @@ def _validate_settings(settings):
     return re.fullmatch(_gen_settings_regex(), settings) is not None
 
 
+def _invalid_settings_err_msg(settings):
+    entities = "\n  " + "\n  ".join(
+        itertools.chain(
+            log_registry.log_alias_to_log_qname.keys(), log_registry.artifact_names
+        )
+    )
+    msg = (
+        f"Invalid log settings: {settings}, must be a comma separated list of fully qualified module names, "
+        f"registered log names or registered artifact names.\nCurrently registered names: {entities}"
+    )
+    return msg
+
+
 @functools.lru_cache()
 def _parse_log_settings(settings):
     if settings == "":
         return dict()
 
     if not _validate_settings(settings):
-        raise ValueError(
-            f"Invalid log settings: {settings}, must be a comma separated list of registerered log or artifact names."
-        )
+        raise ValueError(_invalid_settings_err_msg(settings))
 
     settings = re.sub(r"\s+", "", settings)
     log_names = settings.split(",")
@@ -295,9 +306,7 @@ def get_name_level_pair(name):
                 log_registry.register_child_log(name)
             log_state.enable_log(name, level)
         else:
-            raise ValueError(
-                f"Invalid log settings: '{settings}', must be a comma separated list of log or artifact names."
-            )
+            raise ValueError(_invalid_settings_err_msg(settings))
 
     return log_state