fix: menu icon inoperative

[xiaohuoni]

Close: umijs/umi#4483

支持旧的写法

{
        path: '/',
        component: '@/pages/index',
        menu: { // 兼容此写法
            name: '欢迎',
            icon: 'smile',
        }
}

[codecov]

Codecov Report

Merging #168 into master will decrease coverage by 0.07%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #168      +/-   ##
==========================================
- Coverage   51.60%   51.53%   -0.08%     
==========================================
  Files          63       63              
  Lines        1430     1432       +2     
  Branches      401      419      +18     
==========================================
  Hits          738      738              
- Misses        692      694       +2     

Impacted Files	Coverage Δ
packages/plugin-layout/src/index.ts	0.00% <0.00%> (ø)

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[sorrycc]

老的迁移下？

[xiaohuoni]

老的迁移下？

这有点不好说。预计 issues 会比较多。给说明的话，可以考虑关闭。现在的 menu 配置，都是有效的，只是这个 icon 没被转化。如果要不兼容旧的写法，那要考虑全部删除 menu 配置，不然支持 menu 配置，只是不支持 menu 配置 icon 。感觉不太合理。

[chenshuai2144]

menu:{} 这个配置是应该兼容一下