[MLIR] Fix operand type in `from_extent_tensor` in the shape dialect

[frgossen]

Summary

The operand of from_extent_tensor is now of the same index type as the result
type of the inverse operation to_extent_tensor.

Depends On D80281

[herhut]

I believe we have some use cases where extent tensors are i32 due to early lowering out of index type. @mravishankar might know how this is done in IREE. In the HLO dialect, we have the ScalarsToDimensionTensor op and that allows integer types and index.

In any case, the two ops should agree on their supported types.

[silvas]

Thanks, this is a great cleanup! I happen to have added this before tensor<index> was allowed so I used i32, but now that doesn't make sense.

[herhut]

Seems @silvas thinks this is ok, so I assume it will also work for IREE. Feel free go ahead an land.

[frgossen]

Rebase

mlir/include/mlir/Dialect/Shape/IR/ShapeOps.td

 def Shape_FromExtentTensorOp : Shape_Op<"from_extent_tensor", []> {
   let summary = "Creates a shape from a tensor of extents";
   let description = [{
     Creates a shape from a 1D integral tensor of extents. The rank of the
     resulting shape equals the number of elements in the tensor, and the
     extents match the values of the elements.
   }];
 
-  let arguments = (ins I32Tensor:$input);
+  let arguments = (ins IndexTensor:$input);
   let results = (outs Shape_ShapeType:$result);
 }
 
 def Shape_ToExtentTensorOp : Shape_Op<"to_extent_tensor", []> {
   let summary = "Creates a dimension tensor from a shape";
   // TODO: Think more about the error situation. Perhaps factor out the
   // error detection into a separate op so downstream consumers can control
   // their error behavior. Then this op would assume that the input has