Do not add explicit reshards for ReverseOp.

[copybara-service]

Do not add explicit reshards for ReverseOp.

GSPMD partitioner adds extra collective permute when an explicit reshards added for the case that the operand is not sharded but the result is sharded on the reversing dimension.

Hence, for the moment, turn off explicit reshard inserting for ReverseOp.

Comparing the output of GSPMD partitioner for:

func.func @main(%arg0: tensor<4x32xf32> [{}, {}]) {
  %0 = stablehlo.reverse %arg0, dims = [1] {
    sdy.sharding = [{}, {"x"}],
    sdy.sharding_rule = ([i, j])->([i, j])}
  : tensor<4x32xf32>
  return %0 : tensor<4x32xf32>
} -> tensor<4x32xf32> [{}, {"x"}]

vs

func.func @main(%arg0: tensor<4x32xf32> [{}, {}]) {
  %0 = sdy.reshard %arg0 [{}, {"x"}]
  %1 = stablehlo.reverse %0, dims = [1] {
    sdy.sharding = [{}, {"x"}],
    sdy.sharding_rule = ([i, j])->([i, j])}
  : tensor<4x32xf32>
  return %1 : tensor<4x32xf32>
} -> tensor<4x32xf32> [{}, {"x"}]

GSPMD partitioner outputs the following diff:

ENTRY %main.6_spmd (param: f32[4,32]) -> f32[4,16] {
  %param = f32[4,32]{1,0} 
    parameter(0), 
    sharding={replicated}

  %constant.1 = s32[] constant(0)
  %constant.2 = s32[2]{0} constant({0, 16})
  < %constant = u32[8]{0} constant({1, 1, 1, 1, 0, 0, 0, 0})
  > %constant = u32[8]{0} constant({0, 0, 0, 0, 1, 1, 1, 1})
  %partition-id = u32[] partition-id()
  %dynamic-slice = u32[1]{0} 
    dynamic-slice(u32[8]{0} %constant, u32[] %partition-id),
    dynamic_slice_sizes={1}
  %reshape = u32[] 
    reshape(u32[1]{0} %dynamic-slice)
  %dynamic-slice.1 = s32[1]{0} 
    dynamic-slice(s32[2]{0} %constant.2, u32[] %reshape),
    dynamic_slice_sizes={1}
  %reshape.1 = s32[] reshape(s32[1]{0} %dynamic-slice.1)
  %dynamic-slice.2 = f32[4,16]{1,0} 
    dynamic-slice(f32[4,32]{1,0} %param, s32[] %constant.1, s32[] %reshape.1),
    dynamic_slice_sizes={4,16}

  < ROOT %reverse.0 = f32[4,16]{1,0}
      reverse(f32[4,16]{1,0} %dynamic-slice.2)
  > %collective-permute = f32[4,16]{1,0} 
      collective-permute(f32[4,16]{1,0} %dynamic-slice.2), 
      channel_id=1,
      source_target_pairs={{0,4},{1,5},{2,6},{3,7},{4,0},{5,1},{6,2},{7,3}}
  > ROOT %reverse.0 = f32[4,16]{1,0} 
      reverse(f32[4,16]{1,0} %collective-permute), 
      dimensions={1}