[mlir][Linalg] Add a linalg.tensor_reshape to operate on tensors

Summary:
This revision adds a tensor_reshape operation that operates on tensors.
In the tensor world the constraints are less stringent and we can allow more
arbitrary dynamic reshapes, as long as they are contractions.

The expansion of a dynamic dimension into multiple dynamic dimensions is under-specified and is punted on for now.

Differential Revision: https://reviews.llvm.org/D77360