Add XML documentation for Android.Locations.Provider

The `Android.Locations.Provider` namespace contains **94** `To be added` placeholders in source XML documentation (excluding `docs\xml\index.xml`).

Example command:

```powershell
rg -n -i --glob 'Android.Locations.Provider/**' --glob 'ns-Android.Locations.Provider.xml' 'to be added' docs\xml
```

## Update log

- 2026-09-10: Refreshed the placeholder scan from **92** to **94** (increased by **2**). Related documentation PRs: [#644](https://github.com/dotnet/android-api-docs/pull/644).

Run the provided rg command against docs\xml to list the 94 placeholders under Android.Locations.Provider, excluding docs\xml\index.xml. Review the matching XML documentation entries and replace the placeholders with accurate documentation. Done means the namespace scan no longer reports those "To be added" entries.

索引モデルが issue の本文から書いたものです。