Unit test: Add reporter watermark configuration to angular.json

### Command

test

### Description

After taking advantage of all the new Vitest unit test features in 21.0.0, there is only one configuration item left in the vitest-base.config.ts:

```
export default defineConfig({
test: {
slowTestThreshold: 1000
}
});
```

This is required since the Vitest's [slowTestThreshold](https://vitest.dev/guide/cli.html#slowtestthreshold) default of 300 ms is not adequate for extended test cases.

Ideally this configuration should be available through the angular.json configuration unit-test options, since it would allow the complete removal of the vitest-base.config.ts file.

Maybe follow the nomenclature that you introduced with "coverageWatermarks" and call it "reporterWatermark".

### Describe the solution you'd like

_No response_

### Describe alternatives you've considered

_No response_

先从 angular.json 中的单元测试选项和 vitest-base.config.ts 开始，然后运行仓库的单元测试命令，以追踪选项如何传递到 Vitest。确认所需的慢测试阈值设置可通过 angular.json 接受，并且可以移除 vitest-base.config.ts 而不会丢失配置。

由索引模型根据 Issue 内容生成。