update: Uses SmallInteger type for IntEnum

Updates the `IntEnum` SQLAlchemy type to `SmallInteger`.

This change reduces the storage size required for `IntEnum` columns when the full range of `Integer` is not needed.

Author: KunxiSun

sqlmodel/sql/sqltypes.py

@@ -65,7 +65,7 @@ def load_dialect_impl(self, dialect: Dialect) -> "types.TypeEngine[Any]":
 
 _TIntEnum = TypeVar("_TIntEnum", bound="_IntEnum")
 class IntEnum(types.TypeDecorator[Optional[_TIntEnum]]):
-    impl = types.Integer
+    impl = types.SmallInteger
     cache_ok = True
 
     def __init__(self, enum_type: type[_TIntEnum], *args: Any, **kwargs: Any):