Role Assignment with different `name` wasn't detected

**Describe the bug**
Role Assignment with different `name` wasn't detected as a change.

**To Reproduce**
Steps to reproduce the behavior:
1. In Azure Portal, manually create role assignment on an App Config Service for an APIM
2. In a bicep deployment script, define that same role assignment using a GUID that is generated from the `guid` function.
3. Run `New-AzDeployment` passing the bicep template file and with `-WhatIf:True`
4. WhatIf doesn't list the role assignment as being different
5. If you run `New-AzDeployment` passing the bicep template file and **without** `-WhatIf:True`, the deployment will fail with "role assignment already exists" similar to this issue https://github.com/Azure/azure-quickstart-templates/issues/4205

**Expected behavior**
If the deployment would result in an error, then whatif should fail to validate

**Screenshots**
If applicable, add screenshots to help explain your problem.

**Client** [e.g. PowerShell, CLI, API)
PowerShell

**Additional context**
Add any other context about the problem here.

Reproduce the issue by creating the role assignment in Azure Portal, defining it in a Bicep deployment with a generated GUID, and running New-AzDeployment with -WhatIf. Compare the existing and declared role assignment names, then verify that What-If reports the conflict or validation failure that causes the real deployment to fail.

Written by the indexing model from the issue text.