[MLIR][Python] Add encoding argument to tensor.empty Python function (#110656)

Hi @xurui1995 @makslevental,

I think in llvm/llvm-project#103087 there's
unintended regression where user can no longer create sparse tensors
with `tensor.empty`.

Previously I could pass:
```python
out = tensor.empty(tensor_type, [])
```
where `tensor_type` contained `shape`, `dtype`, and `encoding`.

With the latest 
```python
tensor.empty(sizes: Sequence[Union[int, Value]], element_type: Type, *, loc=None, ip=None)
```
it's no longer possible.

I propose to add `encoding` argument which is passed to
`RankedTensorType.get(static_sizes, element_type, encoding)` (I updated
one of the tests to check it).

Author: mtsokol

mlir/python/mlir/dialects/tensor.py

@@ -1,6 +1,7 @@
 #  Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 #  See https://llvm.org/LICENSE.txt for license information.
 #  SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+from typing import Optional
 
 from ._tensor_ops_gen import *
 from ._tensor_ops_gen import _Dialect
@@ -25,6 +26,7 @@ def __init__(
         sizes: Sequence[Union[int, Value]],
         element_type: Type,
         *,
+        encoding: Optional[Attribute] = None,
         loc=None,
         ip=None,
     ):
@@ -40,19 +42,22 @@ def __init__(
             else:
                 static_sizes.append(ShapedType.get_dynamic_size())
                 dynamic_sizes.append(s)
-        result_type = RankedTensorType.get(static_sizes, element_type)
+        result_type = RankedTensorType.get(static_sizes, element_type, encoding)
         super().__init__(result_type, dynamic_sizes, loc=loc, ip=ip)
 
 
 def empty(
     sizes: Sequence[Union[int, Value]],
     element_type: Type,
     *,
+    encoding: Optional[Attribute] = None,
     loc=None,
     ip=None,
 ) -> _ods_cext.ir.Value:
     return _get_op_result_or_op_results(
-        EmptyOp(sizes=sizes, element_type=element_type, loc=loc, ip=ip)
+        EmptyOp(
+            sizes=sizes, element_type=element_type, encoding=encoding, loc=loc, ip=ip
+        )
     )