Set-AzApiManagementPolicy for policy fragments

### Description

It does not seem possible to upload policy fragments with Set-AzApiManagementPolicy; I'd expect to find this on this page:
https://learn.microsoft.com/en-us/powershell/module/az.apimanagement/set-azapimanagementpolicy?view=azps-10.4.1

When will this be supported?

I'd expect to have something like the tenant policy command, see the suggestion in the script example.

### Script or Debug output

```PowerShell
Set-AzApiManagementPolicy `
-Context $ApiMgmtContext `
-PolicyFilePath $xmlPath `
-Type "Fragment"
```

### Environment data

```PowerShell
PSVersion 7.3.8 - PSEdition Core
```

### Module versions

```PowerShell
Az.ApiManagement 4.0.2
```

### Error output

_No response_