[inductor][ez] return choicecallers directly (#161345)

# why

- remove repeat patterns
- we have everything to make the choicecallers
  - templates
  - input_nodes
  - layouts
  - all the kwargs

# what

- yield a choicecaller directly from V.choices.get_mm_configs

# testing

```
python3 -bb -m pytest test/inductor/test_max_autotune.py -v
```

Differential Revision: [D81520577](https://our.internmc.facebook.com/intern/diff/D81520577)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/161345
Approved by: https://github.com/jansel
ghstack dependencies: #162075, #161340, #161341, #161342, #161343, #161344

torch/_inductor/select_algorithm.py

@@ -1919,6 +1919,18 @@ class ExternKernelChoice:
         # unique by prefixing with aten
         return f"aten::{self.name}"
 
+    def choice_or_none(self, **kwargs: Any) -> Optional[ChoiceCaller]:
+        """
+        Maybe generates a new ChoiceCaller and returns it, or None if generation fails.
+
+        kwargs: Additional kwargs to be passed to generate a new ChoiceCaller.
+        """
+        temp_choices: list[Any] = []
+        result = self.maybe_append_choice(temp_choices, **kwargs)
+        if result is None and len(temp_choices) == 1:
+            return temp_choices[0]
+        return None
+
     def maybe_append_choice(
         self, choices: list[Any], **kwargs: Any
     ) -> Optional[NotImplementedError]: