Missing DefaultDllImportSearchPaths attribute in WindowsAppRuntime_EnsureIsLoaded when WindowsAppSDKSelfContained is turned on

### Describe the bug

When both `WindowsAppSDKSelfContained` and code analysis are turned on for a WinUI 3 project, it fails to build due to
[CA5392: Use DefaultDllImportSearchPaths attribute for P/Invokes](https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/quality-rules/ca5392) in `Microsoft.Windows.Foundation.UndockedRegFreeWinRTCS.WindowsAppRuntime_EnsureIsLoaded`.


### Steps to reproduce the bug

1. Create a WinUI 3 project (either packaged with single project or with WAP).
2. Add `true` in the project file.
3. Turn on code analysis with the following project properties:
``` true
all
latest
true
true
```
4. Build the project.

See example code repo here: https://github.com/[aries-zhang/WinUI3-Publish-SelfContained](https://github.com/aries-zhang/WinUI3-Publish-SelfContained)

### Expected behavior

1. Build should be successful.
2. No potential DLL hijacking risks should present.

### Screenshots


### NuGet package version

WinUI 3 - Windows App SDK 1.6.1: 1.6.240923002

### Windows version

Windows 11 (24H2): Build 22621

### Additional context

Since this is generated code (or included from Nuget?), it makes it hard to suppress the error individually if not a global suppression rule.