Delete chlo.dynamic_reshape
Delete chlo.dynamic_reshape

Deleting this op is part of the StableHLO Dynamism 101 RFC: https://github.com/openxla/stablehlo/blob/main/rfcs/20230704-dynamism-101.md#-p1-move-tensorflow-specific-operations-out-of-stablehlo

AFAICT, the only remaining use of this op is in the legalization for tf.reshape.

In a future change, I will delete [ms]hlo.compute_reshape_shape and [ms]hlo.cstr_reshapable as well.

I kept the DRR pattern so I could restrict the source pattern to when
the tensor argument is an MHLO_Tensor. However, because the result pattern contains
an op with a region (shape.assuming), I used a NativeCodeCall to implement the
conversion.
