[mlir][Linalg] Put a proper type on transform.structured.match op

This allows much better verification messages in consuming ops that properly declare
`TransformHandleTypeInterface` on their operands.

Downstream tests can be updated with a command resembling:

```
 git grep -l "structured\.match" mlir/test | xargs -i sed -i {} -e  "s/\(structured.match.*\)/\1 : (\!pdl.operation) -> \!pdl.operation/g"
```

Differential Revision: https://reviews.llvm.org/D142643