Add XML documentation for Dalvik.SystemInterop

The `Dalvik.SystemInterop` namespace contains **85** `To be added` placeholders in source XML documentation (excluding `docs\xml\index.xml`).

```powershell
rg -n -i --glob 'Dalvik.SystemInterop/**' --glob 'ns-Dalvik.SystemInterop.xml' 'to be added' docs\xml
```

## Update log

- 2026-09-10: Refreshed the placeholder scan from **126** to **85** (reduced by **41**). Related documentation PRs: [#482](https://github.com/dotnet/android-api-docs/pull/482), [#596](https://github.com/dotnet/android-api-docs/pull/596), [#644](https://github.com/dotnet/android-api-docs/pull/644).

首先对 docs\xml 运行提供的 rg 扫描，以列出剩余的 85 个占位符。检查 Dalvik.SystemInterop 和 ns-Dalvik.SystemInterop.xml 下的匹配项，然后将占位符替换为适当的 XML 文档并重新运行扫描；当 docs\xml\index.xml 之外不再存在匹配的占位符时即表示完成。

由索引模型根据 Issue 内容生成。