fix(input): fix overlapping styles of neighboring components in input-group

[Summer-Shen]

Types of changes

• New feature
• Bug fix
• Enhancement
• Component style change
• Typescript definition change
• Documentation change
• Coding style change
• Refactoring
• Test cases
• Continuous integration
• Breaking change
• Others

Background and context

• 在线性主题下，a-input-group 里面相邻组件的边框叠加的问题，希望可以优化一下 #1737
• 另外，亦参考了这个 issue：线性主题下，优化按钮组-按钮边框hover，active样式的层级问题 #1758

Solution

修改了 input 组件的部分 z-index 和 border-right-color 属性

How is the change tested?

• 由于暂时未能在 acro-design-vue 使用线性主题，通过本地修改一些 vars 验证了提交的效果
• 更新了 input 测试用例

Changelog

Component	Changelog(CN)	Changelog(EN)	Related issues
input	修复 input-group 相邻组件样式叠加时的问题	Fix overlapping styles of neighboring components in input-group	Close #1737 , Close #1758

Checklist:

• Test suite passes (npm run test)
• Provide changelog for relevant changes (e.g. bug fixes and new features) if applicable.
• Changes are submitted to the appropriate branch (e.g. features should be submitted to feature branch and others
  should be submitted to main branch)

Other information

如果之后本地能引入线性主题复现问题，可能会进一步修改

[flsion]

@Summer-Shen 这个 PR 我本地测试了一下，线框模式还是会有问题，不过提供了一个很好的思路，我再完善一下

[flsion]

related #2917