Allow passing --changed cli option to vitest

### Command

test

### Description

The `unit-test` builder does not provide a way to use the `--changed` vitest option: https://vitest.dev/guide/cli.html#changed. This will analyze the import graph and only run tests affected by a change, which is useful for running a subset of the test suite for pull requests. This option is not available through the vitest configuration file.

### Describe the solution you'd like

Add a `changed: ` option to the `unit-test` builder options which passes `--changed ` to the vitest runner.

### Describe alternatives you've considered

I don't think there are any good workarounds. Using `@analogjs/vitest-angular` exposes vitest directly, but requires more setup and is not an "official" package.

从单元测试构建器选项开始，跟踪它们如何传递给 Vitest runner。验证变更后的字符串选项会转发 --changed ，并确保相关的构建器测试覆盖生成的命令。

由索引模型根据 Issue 内容生成。