[FEATURE]: Add multiset host-bulk `contains`

[Yunsong Wang]

Is your feature request related to a problem? Please describe.

Add contains and contains_async APIs

Describe the solution you'd like

Two APIs we want to add:

  /**
   * @brief Indicates whether the keys in the range `[first, last)` are contained in the multiset.
   *
   * @note This function synchronizes the given stream. For asynchronous execution use
   * `contains_async`.
   *
   * @tparam InputIt Device accessible input iterator
   * @tparam OutputIt Device accessible output iterator assignable from `bool`
   *
   * @param first Beginning of the sequence of keys
   * @param last End of the sequence of keys
   * @param output_begin Beginning of the sequence of booleans for the presence of each key
   * @param stream Stream used for executing the kernels
   */
  template <typename InputIt, typename OutputIt>
  void contains(InputIt first,
                InputIt last,
                OutputIt output_begin,
                cuda_stream_ref stream = {}) const;

  /**
   * @brief Asynchronously indicates whether the keys in the range `[first, last)` are contained in
   * the multiset.
   *
   * @tparam InputIt Device accessible input iterator
   * @tparam OutputIt Device accessible output iterator assignable from `bool`
   *
   * @param first Beginning of the sequence of keys
   * @param last End of the sequence of keys
   * @param output_begin Beginning of the sequence of booleans for the presence of each key
   * @param stream Stream used for executing the kernels
   */
  template <typename InputIt, typename OutputIt>
  void contains_async(InputIt first,
                      InputIt last,
                      OutputIt output_begin,
                      cuda_stream_ref stream = {}) const noexcept;

Describe alternatives you've considered

No response

Additional context

• Invoking the OA bass contains should be sufficient. Fairly easy to add.
• Overloads taking custom hasher and comparator are not needed for now

[Daniel Jünger]

closed by #468