Lattigo: multiple encoding of same plaintext would result in duplicated variable name in emitter

[ZenithalHourlyRate]

For the following mlir

  %c1 = arith.constant dense<1> : tensor<4xi16>
  %base0 = arith.addi %base, %c1 : tensor<4xi16>
  %base1 = arith.addi %base0, %c1 : tensor<4xi16>

It will be translated to

  v0 := []int64{1, 1, 1, 1}
  pt := bgv.NewPlaintext(param, param.MaxLevel())
  // v0_packed appearing for the first time
  v0_packed := make([]int64, param.MaxSlots())
  for i := range v0_packed {
    v0_packed[i] = int64(v0[i % len(v0)])
  }
  encoder.Encode(v0_packed, pt) 
  pt1 := pt
  ct2, err0 := evaluator.AddNew(ct, pt1)
  if err0 != nil {
    panic(err0)
  }
  pt2 := bgv.NewPlaintext(param, param.MaxLevel())
  // v0_packed appearing for the second time
  // GO would complain "no new variables on left side of :="
  v0_packed := make([]int64, param.MaxSlots())
  for i := range v0_packed {
    v0_packed[i] = int64(v0[i % len(v0)])
  }
  encoder.Encode(v0_packed, pt2)
  pt3 := pt2 
  ct3, err1 := evaluator.AddNew(ct2, pt3)
  if err1 != nil {
    panic(err1)
  }
  return ct3

Should be fixed by v0_pt_packed and v0_pt2_packed.

Or should be be fixed by CSE? but it seems like the following code could not be CSE, especially different plaintext could have different scale (ref to #1169)

    %cst = arith.constant dense<1> : tensor<4xi16>
    %pt = lattigo.bgv.new_plaintext %param : (!lattigo.bgv.parameter) -> !lattigo.rlwe.plaintext
    %pt_1 = lattigo.bgv.encode %encoder, %cst, %pt : (!lattigo.bgv.encoder, tensor<4xi16>, !lattigo.rlwe.plaintext) -> !lattigo.rlwe.plaintext
    %ct_2 = lattigo.bgv.add %evaluator, %ct, %pt_1 : (!lattigo.bgv.evaluator, !lattigo.rlwe.ciphertext, !lattigo.rlwe.plaintext) -> !lattigo.rlwe.ciphertext
    %pt_3 = lattigo.bgv.new_plaintext %param : (!lattigo.bgv.parameter) -> !lattigo.rlwe.plaintext
    %pt_4 = lattigo.bgv.encode %encoder, %cst, %pt_3 : (!lattigo.bgv.encoder, tensor<4xi16>, !lattigo.rlwe.plaintext) -> !lattigo.rlwe.plaintext
    %ct_5 = lattigo.bgv.add %evaluator, %ct_2, %pt_4 : (!lattigo.bgv.evaluator, !lattigo.rlwe.ciphertext, !lattigo.rlwe.plaintext) -> !lattigo.rlwe.ciphertext