[Triton-MLIR] Replace triton.extract_slice with tensor.extract_slice and support more general tensor slicing (#837)

## Features

- Allow taking a block of tensor slice, as long as each dimension is
contiguous (unit stride).
- Fix some problems in `insert_slice_async`'s semantic.
- More general verification for ops that return shared layout encoding.

## Known Limitations

- `insert_slice_async` still uses the old semantic. May submit another
PR later to support similar semantic like `tensor.extract_slice`.
- No encoding verification for `tensor.extract_slice`.
- 3d tensor ops are broken.
- Strided accesses are not allowed.
- May cause a little performance slowdown since we are passing strides
as values but not constants (e.g., int).
It would be difficult to pass strides as attributes when we have control
flows. A block argument is possible to accept tensors with different
strides.

python/tests/test_elementwise.py

@@ -137,7 +137,7 @@ def kernel(X0, X1, Y, BLOCK: tl.constexpr):
     # reference result
 
     if expr == "cdiv":
-        y_ref = (x0 + x1 - 1) // x1
+        y_ref = torch.div(x0 + x1 - 1, x1, rounding_mode='trunc')
     elif expr == "umulhi":
         y_ref = ((x0.to(torch.int64) * x1) >> 32).to(torch.int32)
     else: