UWP => WinUI3 migration: PasswordVault cannot be accessed anymore

### Describe the bug

We are storing a randomly generated key inside the [PasswordVault](https://learn.microsoft.com/en-us/uwp/api/windows.security.credentials.passwordvault?view=winrt-22621) in order to encrypt and decrypt user data serialized to an xml (for improved security).
This is working fine for both the UWP and the WinUi3 applications on their own.
However, if the user was updating from UWP to WinUi3 application (package friendly name, etc. are identical, whereas the OS also handles this as an update!) the previously stored credentials are no longer retrievable!
Thus any encrypted serialization data in place prior to the update is now lost and no longer usable.

### Steps to reproduce the bug

1. store credentials in [PasswordVault](https://learn.microsoft.com/en-us/uwp/api/windows.security.credentials.passwordvault?view=winrt-22621) within UWP app
2. migrate codebase to WinUi3 (PaswordVault class is still present)
3. install app update
4. try to access the previously stored credentials in the very same app
=> Please note, that no entry will be found.

### Expected behavior

After upgrading app, credentials should still be fetchable.

### Screenshots

The below image depicts the 'Credential Manager' (the above entry is from UWP, and the bottom one was generated within the very same app after migrating to WinUi3):


### NuGet package version

Windows App SDK 1.5.3: 1.5.240428000

### Packaging type

Packaged (MSIX)

### Windows version

Windows 11 version 22H2 (22621, 2022 Update)

### IDE

Visual Studio 2022

### Additional context

_No response_

Reproduce the migration described: store credentials through PasswordVault in the UWP app, upgrade the packaged app to WinUI3, and attempt to retrieve them. Compare the Credential Manager entries shown in the issue and determine whether the missing credentials are caused by identity, packaging, or API behavior. Done means documenting the cause and an upgrade-compatible retrieval path or confirming a platform limitation.

Written by the indexing model from the issue text.