[Package Issue]: Package.Identifier incorrect metadata update for Google.GoogleDesktop

### Please confirm these before moving forward

- [x] I have searched for my issue and not found a work-in-progress/duplicate/resolved issue.
- [x] I have not been informed if the issue is resolved in a preview version of the winget client.

### Category of the issue

Other

### Brief description of your issue

The `Google.GoogleDesktop` package identifier currently conflates two different applications. Recently, the new "Google app for desktop" (v150/v151+) has been added as an update for the old, discontinued "Google Desktop" application (v5.9.x). Because they share a package name, package managers push a destructive upgrade path that overwrites the older app.

### Steps to reproduce

1. Have Google Desktop (v5.9.1005.112335) installed on a Windows PC.
2. Run `winget upgrade` or use e.g. UniGetUI.
3. WinGet flags the legacy installation as outdated and wants to update Google Desktop to the unrelated Google app for desktop, version 151.x.

E.g.:
```
winget list --id Google.GoogleDesktop
Name Id Version Available Source
----------------------------------------------------------------------
Google Desktop Google.GoogleDesktop 5.9.1005.12335 151.0.7910.0 winget
```

### Actual behavior

WinGet attempts to upgrade Google Desktop 5.9.x (which I assume would uninstall it) with an unrelated application due to the shared `Google.GoogleDesktop` ID.

### Expected behavior

The legacy Google Desktop application folder should remain frozen at v5.9.x. The modern application should be split into its own decoupled package identifier (e.g., `Google.GoogleAppForDesktop`).

### Environment

```raw
winget --info
Windows Package Manager v1.29.280
© 2026 Microsoft. All rights reserved.

Windows: Windows.Desktop v10.0.22631.7219
System Architecture: X64
Package: Microsoft.DesktopAppInstaller v1.29.280.0
```

### Screenshots and Logs

See: https://github.com/microsoft/winget-pkgs/tree/master/manifests/g/Google/GoogleDesktop

Start by reviewing the manifests under manifests/g/Google/GoogleDesktop and the package identifier and version metadata for both applications. Check how the legacy Google Desktop installation is matched to the newer release, then verify that the modern application has a separate identifier and that the legacy package no longer presents that upgrade path. Use the issue's reproduction commands to confirm the completed metadata behavior.

Written by the indexing model from the issue text.