Issue(Feature request): Target Host supports the reference of variables in the Environment

## What?
Target Host supports the reference of variables in the Environment

## Why?
Scenario ：
Assuming there are multiple environments for traffic replay, such as UAT01, UAT02, etc., I can configure the corresponding domain name and other required parameters for each environment in the Environment. During replay, variables can be directly referenced


No files, tests, or entry points are named. Start by locating the TypeScript frontend code for Target Host, Environment configuration, and traffic replay, then trace how configured values are passed into replay. Done means a Target Host can reference variables defined for the selected Environment and those references resolve correctly for multiple environments.

Written by the indexing model from the issue text.