[dynamic_shapes] Fix the lowering of shapes in x64 mode.
[dynamic_shapes] Fix the lowering of shapes in x64 mode.

The mhlo.reshape op has the constraint that the operand and the result
must have the same element type. Cast the dimension size to int32 to
meet this constraint even in 64-bit mode.

google/jax,google/jax,google/jax,google/jax