message: [XLA] Make HLO categorization a bit more sane.
  Remove meaningless distinctions between fusion nodes. Knowing whether a loop fusion op is "elementwise" (~ doesn't contain any broadcast inputs) doesn't provide any useful information.
diff: @@ -2258,26 +2258,9 @@ string HloInstruction::ToCategory() const {
  }
  if (opcode() == HloOpcode::kFusion) {
  - if (operands().size() == 2) {
  - bool saw_rank_1 = false;
  - bool saw_higher_rank = false;
  - for (const auto* operand : operands()) {
  - if (!ShapeUtil::IsTuple(operand->shape())) {
  - saw_rank_1 |= ShapeUtil::Rank(operand->shape()) == 1;
  - saw_higher_rank |= ShapeUtil::Rank(operand->shape()) > 1;
  - }
  - }
  - if (saw_rank_1 && saw_higher_rank) {
  - return "rank-1-broadcast binary fusion";
  - }
  - }
  switch (fusion_kind()) {
  case FusionKind::kLoop:
  - if (IsElementwise()) {
  - return "elementwise fusion";
  - } else {
  - return "non-elementwise fusion";
  - }
  + return "loop fusion";
  case FusionKind::kInput:
  return "input fusion";
  case FusionKind::kOutput:
  @@ -2292,7 +2275,7 @@ string HloInstruction::ToCategory() const {
  }
  }
  - if (IsElementwise() && opcode() != HloOpcode::kFusion) {
  + if (IsElementwise()) {
  return "non-fusion elementwise";
  }
  