Peek function and size reporting macros changes.

[arduzilla]

I have added peek function taking the element without removing it from the queue. Also moved and added some size reporting functions

[arduzilla]

/**
 * peek an object from the queue without removing it from the queue, blocking if the queue is already empty
 *
 * @param queue         the queue
 * @param data          the data
 * @param wait_ms       milliseconds to wait
 * @returns RPA_EINTR   the blocking was interrupted (try again)
 * @returns RPA_EOF     if the queue has been terminated
 * @returns RPA_SUCCESS on a successful pop
 */
bool rpa_queue_timedpeek(rpa_queue_t *queue, void **data, int wait_ms);

/**
 * @brief Macro to check if the rpa_queue_t is full.
 *
 * This macro checks if the number of elements in the queue is equal to the maximum
 * size of the queue, indicating that the queue is full.
 *
 * @param queue Pointer to the rpa_queue_t instance.
 * @return 1 if the queue is full, 0 otherwise.
 */
#define rpa_queue_full(queue) ((queue)->nelts == (queue)->bounds)

/**
 * @brief Macro to get the number of free slots in the rpa_queue_t.
 *
 * This macro calculates the number of free slots in the queue by subtracting
 * the current number of elements from the maximum size of the queue.
 *
 * @param queue Pointer to the rpa_queue_t instance.
 * @return The number of free slots in the queue.
 */
#define rpa_queue_get_free(queue) (((queue)->bounds) - ((queue)->nelts))

/**
 * @brief Macro to get the number of taken slots in the rpa_queue_t.
 *
 * This macro retrieves the current number of elements in the queue, indicating
 * the number of slots that have been taken.
 *
 * @param queue Pointer to the rpa_queue_t instance.
 * @return The number of taken slots in the queue.
 */
#define rpa_queue_get_taken(queue) ((queue)->nelts)

/**
 * @brief Macro to check if the rpa_queue_t is empty.
 *
 * This macro checks if the number of elements in the queue is zero, indicating
 * that the queue is empty.
 *
 * @param queue Pointer to the rpa_queue_t instance.
 * @return 1 if the queue is empty, 0 otherwise.
 */
#define rpa_queue_empty(queue) ((queue)->nelts == 0)