function setHoverStyle(el, hoverStyle) {
    setAsHighDownDispatcher(el, true);
    traverseUpdate(el, setElementHoverStyle, hoverStyle);
}
See more info in `setTextStyleCommon`.
@param {Object|module:zrender/graphic/Style} normalStyle
@param {Object} emphasisStyle
@param {module:echarts/model/Model} normalModel
@param {module:echarts/model/Model} emphasisModel
@param {Object} opt Check `opt` of `setTextStyleCommon` to find other props.
@param {string|Function} [opt.defaultText]
@param {module:echarts/model/Model} [opt.labelFetcher] Fetch text by
     `opt.labelFetcher.getFormattedLabel(opt.labelDataIndex, 'normal'/'emphasis', null, opt.labelDimIndex)`
@param {module:echarts/model/Model} [opt.labelDataIndex] Fetch text by
     `opt.textFetcher.getFormattedLabel(opt.labelDataIndex, 'normal'/'emphasis', null, opt.labelDimIndex)`
@param {module:echarts/model/Model} [opt.labelDimIndex] Fetch text by
     `opt.textFetcher.getFormattedLabel(opt.labelDataIndex, 'normal'/'emphasis', null, opt.labelDimIndex)`
@param {Object} [normalSpecified]
@param {Object} [emphasisSpecified]