环境变量多函数之间共享

如果一组环境变量多于多个函数都是一样，在 template.yml 会出现重复配置的问题，建议提供一种机制可以较少冗余，让维护和修改更方便。

Start by tracing how environment variables for multiple functions are represented and processed from template.yml. Compare the repeated configurations and define a shared form that preserves each function's settings; done means the template no longer needs identical environment-variable blocks and the generated function configuration remains correct.

Written by the indexing model from the issue text.