Add XML documentation for Android.Health.Connect.ChangeLog

The `Android.Health.Connect.ChangeLog` namespace contains **194** `To be added` placeholders in source XML documentation (excluding `docs\xml\index.xml`).

Example command:

```powershell
rg -n -i --glob 'Android.Health.Connect.ChangeLog/**' --glob 'ns-Android.Health.Connect.ChangeLog.xml' 'to be added' docs\xml
```

## Update log

- 2026-09-10: Refreshed the placeholder scan from **147** to **194** (increased by **47**). Related documentation PRs: [#644](https://github.com/dotnet/android-api-docs/pull/644).

Start by running the provided rg command against docs\xml to enumerate the 194 `To be added` entries under Android.Health.Connect.ChangeLog, excluding docs\xml\index.xml. Read the surrounding XML documentation and relevant API names before replacing each placeholder with accurate descriptions; done means the scan returns no remaining placeholders in that namespace.

Written by the indexing model from the issue text.