Add XML documentation for Org.Apache.Http.Cookies

The `Org.Apache.Http.Cookies` namespace contains **83** `To be added` placeholders in source XML documentation (excluding `docs\xml\index.xml`).

```powershell
rg -n -i --glob 'Org.Apache.Http.Cookies/**' --glob 'ns-Org.Apache.Http.Cookies.xml' 'to be added' docs\xml
```

## Update log

- 2026-09-10: Refreshed the placeholder scan from **86** to **83** (reduced by **3**). Related documentation PRs: [#556](https://github.com/dotnet/android-api-docs/pull/556), [#644](https://github.com/dotnet/android-api-docs/pull/644).

Start by running the provided rg command against docs\xml to confirm the current 83-placeholder scope, excluding docs\xml\index.xml. Read the matching Org.Apache.Http.Cookies source XML documentation entries and replace each “To be added” placeholder with accurate documentation. Done means the scoped scan finds no remaining placeholders.

Vom Indexierungsmodell aus dem Issue-Text verfasst.