[Feature] template.yml支持环境变量展开

在线上部署、CI和本地测试环境下，需要设置不同的EnvironmentVariables、CodeUri等。有时候需要通过EnvironmentVariables传入密钥之类的敏感信息，这样就不能直接把环境变量硬编码到template.yml中，上传到代码仓库。这就需要template.yml支持环境变量的展开。

Start by tracing how template.yml is parsed and how EnvironmentVariables and CodeUri are resolved. Define the supported environment-variable expansion behavior for both fields, then add coverage for the expected substitutions and confirm that unresolved or sensitive values are handled as intended.

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