[component][net][update]添加优先网卡配置选项

[Shadowyingjian]

拉取/合并请求描述：(PR description)

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• 添加优先网卡配置选项，在网卡自动切换时可以实现：
  • 1.当优先网卡 linkup 时把优先网卡配置为默认网卡用于上网
  • 2.当优先网卡 linkdown 时自动切换其他能上网的网卡。

]

当前拉取/合并请求的状态 Intent for your PR

必须选择一项 Choose one (Mandatory):

• 本拉取/合并请求是一个草稿版本 This PR is for a code-review and is intended to get feedback
• 本拉取/合并请求是一个成熟版本 This PR is mature, and ready to be integrated into the repo

代码质量 Code Quality：

我在这个拉取/合并请求中已经考虑了 As part of this pull request, I've considered the following:

• 已经仔细查看过代码改动的对比 Already check the difference between PR and old code
• 代码风格正确，包括缩进空格，命名及其他风格 Style guide is adhered to, including spacing, naming and other styles
• 没有垃圾代码，代码尽量精简，不包含#if 0代码，不包含已经被注释了的代码 All redundant code is removed and cleaned up
• 所有变更均有原因及合理的，并且不会影响到其他软件组件代码或BSP All modifications are justified and not affect other components or BSP
• 对难懂代码均提供对应的注释 I've commented appropriately where code is tricky
• 代码是高质量的 Code in this PR is of high quality
• 已经使用formatting等源码格式化工具确保格式符合RT-Thread代码规范 This PR complies with RT-Thread code specification

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[Shadowyingjian]

邮件已收到，谢谢！——来自QQ邮箱客户端

[BernardXiong]

这个补丁是为了解决什么问题？感觉这类会更和工程相关，为什么需要PR这个？