[C++][Parquet] Minor: making parquet TypedComparator operation as const method

[mapleFU]

Describe the enhancement requested

/// \brief Interface for comparison of physical types according to the
/// semantics of a particular logical type.
template <typename DType>
class TypedComparator : public Comparator {
 public:
  using T = typename DType::c_type;

  /// \brief Scalar comparison of two elements, return true if first
  /// is strictly less than the second
  virtual bool Compare(const T& a, const T& b) = 0;

  /// \brief Compute maximum and minimum elements in a batch of
  /// elements without any nulls
  virtual std::pair<T, T> GetMinMax(const T* values, int64_t length) = 0;

  /// \brief Compute minimum and maximum elements from an Arrow array. Only
  /// valid for certain Parquet Type / Arrow Type combinations, like BYTE_ARRAY
  /// / arrow::BinaryArray
  virtual std::pair<T, T> GetMinMax(const ::arrow::Array& values) = 0;

  /// \brief Compute maximum and minimum elements in a batch of
  /// elements with accompanying bitmap indicating which elements are
  /// included (bit set) and excluded (bit not set)
  ///
  /// \param[in] values the sequence of values
  /// \param[in] length the length of the sequence
  /// \param[in] valid_bits a bitmap indicating which elements are
  /// included (1) or excluded (0)
  /// \param[in] valid_bits_offset the bit offset into the bitmap of
  /// the first element in the sequence
  virtual std::pair<T, T> GetMinMaxSpaced(const T* values, int64_t length,
                                          const uint8_t* valid_bits,
                                          int64_t valid_bits_offset) = 0;
};

Current they're all non-const functions. So we need to making them as const.

Component(s)

C++, Parquet