Normalize API feature item

@inner
@param {*} item the feature item to normalize
@param {Object} existed the added feature item map
@param {Array.<Object>} result the normalized feature items result
@param {Object} logger logger the logger utilities
function normalizeFeatureItem(item, existed, result, logger) {
    let addItem;
    if (typeof item === 'string') {
        addItem = addFeatureItem(logger, existed, item);
    }
    else if (Array.isArray(item)) {
        let [name, params] = item;
        addItem = addFeatureItem(logger, existed, name, params);
    }
    else if (item && typeof item === 'object') {
        let {name, params} = item;
        addItem = addFeatureItem(logger, existed, name, params);
    }

    if (addItem) {
        result.push(addItem);
    }
}