feat: Variable splitting use jsonpath-ng.ext and upgrade jsonpath-ng to 1.8.0

[wangliang181230]

What this PR does / why we need it?

1. feat: Variable splitting use jsonpath-ng.ext
   新特性：变量拆分 使用 jsonpath-ng 的扩展功能。
2. 提示信息中，添加 jsonpath-ng 的使用说明页面链接，供使用参考
3. upgrade: jsonpath-ng to 1.8.0

Summary of your change

1. 更新内容：
   变量拆分 节点 可以使用 jsonpath-ng 的扩展函数功能了，详情见 https://pypi.org/project/jsonpath-ng/1.8.0/#extensions
   1.8.0版本增加了两个新的扩展功能：keys 和 str()

2. 截图：

   1. 配置截图：
   
   2. 执行结果图：
   
   3. 提示链接截图：
   

Please indicate you've done the following:

• Made sure tests are passing and test coverage is added if needed.
• Made sure commit message follow the rule of Conventional Commits specification.
• Considered the docs impact and opened a new docs issue or PR with docs changes if needed.

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