【性能调优】图片异步加载：界面切换不白屏的加载策略

---图片的异步加载与占位替换
local loadingTasks = {}
function asyncImageLoad(widget, imagePath, placeholder)
    GUI:Image_loadTexture(widget, placeholder)
    local taskId = "img_" .. imagePath
    if loadingTasks[taskId] then return end
    loadingTasks[taskId] = true
    SL:ScheduleOnce(function()
        local ok = pcall(function()
            GUI:Image_loadTexture(widget, imagePath)
        end)
        loadingTasks[taskId] = nil
    end, 0)
end

---缓存命中的秒回与优先级队列
function asyncImageCached(widget, imagePath)
    if imageCache[imagePath] then
        GUI:Image_loadTexture(widget, imagePath)
        return
    end
    asyncImageLoad(widget, imagePath, "loading.png")
    priorityQueue.push(imagePath, widgetPriority[widget])
    imageCache[imagePath] = true
end