Add getattr overload variants to help mypy type inference (#6355)

These silence errors about missing type annotations for calls
like these:

```
x = getattr(o, 'a', [])
y = getattr(o, 'b', {})
```

This is basically a generalization of #5518 and other overloads we already
have.

This works around python/mypy#11572. I encountered the issue in several
places when testing recent typeshed against an internal repo.

stdlib/@python2/__builtin__.pyi

@@ -850,13 +850,18 @@ def format(__value: object, __format_spec: str = ...) -> str: ...  # TODO unicod
 @overload
 def getattr(__o: Any, name: Text) -> Any: ...
 
-# While technically covered by the last overload, spelling out the types for None and bool
-# help mypy out in some tricky situations involving type context (aka bidirectional inference)
+# While technically covered by the last overload, spelling out the types for None, bool
+# and basic containers help mypy out in some tricky situations involving type context
+# (aka bidirectional inference)
 @overload
 def getattr(__o: Any, name: Text, __default: None) -> Any | None: ...
 @overload
 def getattr(__o: Any, name: Text, __default: bool) -> Any | bool: ...
 @overload
+def getattr(__o: object, name: str, __default: list[Any]) -> Any | list[Any]: ...
+@overload
+def getattr(__o: object, name: str, __default: dict[Any, Any]) -> Any | dict[Any, Any]: ...
+@overload
 def getattr(__o: Any, name: Text, __default: _T) -> Any | _T: ...
 def globals() -> Dict[str, Any]: ...
 def hasattr(__obj: Any, __name: Text) -> bool: ...

stdlib/@python2/builtins.pyi

@@ -850,13 +850,18 @@ def format(__value: object, __format_spec: str = ...) -> str: ...  # TODO unicod
 @overload
 def getattr(__o: Any, name: Text) -> Any: ...
 
-# While technically covered by the last overload, spelling out the types for None and bool
-# help mypy out in some tricky situations involving type context (aka bidirectional inference)
+# While technically covered by the last overload, spelling out the types for None, bool
+# and basic containers help mypy out in some tricky situations involving type context
+# (aka bidirectional inference)
 @overload
 def getattr(__o: Any, name: Text, __default: None) -> Any | None: ...
 @overload
 def getattr(__o: Any, name: Text, __default: bool) -> Any | bool: ...
 @overload
+def getattr(__o: object, name: str, __default: list[Any]) -> Any | list[Any]: ...
+@overload
+def getattr(__o: object, name: str, __default: dict[Any, Any]) -> Any | dict[Any, Any]: ...
+@overload
 def getattr(__o: Any, name: Text, __default: _T) -> Any | _T: ...
 def globals() -> Dict[str, Any]: ...
 def hasattr(__obj: Any, __name: Text) -> bool: ...