feat: popup 关联组件增加 z-index 属性

[eiinu]

这个 PR 做了什么? (简要描述所做更改)

这个 PR 是什么类型? (至少选择一个)

• 新特性提交
• 日常 bug 修复
• 站点、文档改进
• 演示代码改进
• 组件样式/交互改进
• TypeScript 定义更新
• 包体积优化
• 性能优化
• 功能增强
• 国际化改进
• 代码重构
• 代码风格优化
• 测试用例
• 分支合并
• 其他改动（是关于什么的改动？）

这个 PR 涉及以下平台:

• NutUI 4.0 H5
• NutUI 4.0 小程序
• NutUI 3.0 H5
• NutUI 3.0 小程序

这个 PR 是否已自测:

• 自测 Vite 脚手架使用 测试仓库
• 自测 Taro 脚手架使用小程序 & Taro-H5 测试仓库

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (1a17233) 84.94% compared to head (14cff56) 84.97%.
Report is 2 commits behind head on v4.

Additional details and impacted files

@@            Coverage Diff             @@
##               v4    #2632      +/-   ##
==========================================
+ Coverage   84.94%   84.97%   +0.02%     
==========================================
  Files         152      152              
  Lines       21193    21207      +14     
  Branches     2386     2386              
==========================================
+ Hits        18002    18020      +18     
+ Misses       3186     3182       -4     
  Partials        5        5              

Files	Coverage Δ
src/packages/__VUE/actionsheet/index.vue	96.52% <100.00%> (+0.02%)	⬆️
src/packages/__VUE/address/index.vue	88.36% <100.00%> (+0.02%)	⬆️
src/packages/__VUE/cascader/index.vue	91.60% <100.00%> (+0.06%)	⬆️
src/packages/__VUE/dialog/index.vue	95.23% <100.00%> (+0.02%)	⬆️
src/packages/__VUE/sku/index.vue	87.78% <100.00%> (+0.09%)	⬆️

... and 1 file with indirect coverage changes

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