Managing large amounts of environment variables

### Command

build, serve, test, e2e

### Description

I am reopening https://github.com/angular/angular-cli/issues/4318.

Essentially we need a way to pass environment variables to the build/serve commands. environments.ts file is not a viable solution as you would need to end up with hundreds of environment.ts files depending on all the permutations per environment.

The solution to https://github.com/angular/angular-cli/issues/4318 also does not address this since you need to know the `define` values when running the command `ng build ....`
Which means you would have to generate the build command same way as generating the `environment.ts` file.

Most enterprise angular applications I have worked on ends up extending the `webpack.config.js` file adding:
```javascript
DefinePlugin({
process: {
env: {
VAR_1: JSON.stringify(process.env.VAR_1),
...
}
}
})
```

This issue has been brought up for years with the Angular repo but i've never seen a resolution so I want to try to make it as clear as possible.
We should support a `dotenv()` style solution where in the code we can use `process.env.VARIABLE`.
In the build machine we can either:
`export VARIABLE=test`
or have a `.env` file to pick it up.

This is supported by pretty much every other framework out there so I'm not sure why it wouldn't be possible or hasn't already been implemented.

If the issue is the angular team doesn't want this behaviour then that is fine but I am looking for a yes/no type answer. If the answer is no the angular team would be able to point to this issue for all future feature requests of this nature.

### Describe the solution you'd like

_No response_

### Describe alternatives you've considered

_No response_

從之前的 issue #4318 以及 build、serve、test 和 e2e 命令的入口點開始。檢視現有的 environments.ts 作法和 webpack.config.js 中的 DefinePlugin 範例，然後確定應如何將匯出的變數或 .env 檔案公開為 process.env.VARIABLE。當這些命令支援的行為和範圍都已定義時，即視為完成。

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