Convert the property policyId of type ResourceIdentifier to type String in ProtectedItem.

[mcgallan]

Fix : #47381

[azure-sdk]

API change check

APIView has identified API level changes in this PR and created following API reviews.

Azure.ResourceManager.RecoveryServicesBackup

[ArcturusZhang]

I would like a clarification:
in the issue, the only case of this issue is that the value is an empty string, in other cases, this property is a proper arm-id, is this the case?
If so, maybe we could try this configuration first? https://github.com/Azure/autorest.csharp/blob/a7d1bd59aeb5ab28a081ebeef06c2adb167bd983/src/AutoRest.CSharp/Common/Input/Configuration.cs#L47C67-L47C103
and if this does not work, we could add a deserialization hook to that property to make sure we do an empty string check first and then construct the ResourceIdentifier

[mcgallan]

I would like a clarification: in the issue, the only case of this issue is that the value is an empty string, in other cases, this property is a proper arm-id, is this the case? If so, maybe we could try this configuration first? https://github.com/Azure/autorest.csharp/blob/a7d1bd59aeb5ab28a081ebeef06c2adb167bd983/src/AutoRest.CSharp/Common/Input/Configuration.cs#L47C67-L47C103 and if this does not work, we could add a deserialization hook to that property to make sure we do an empty string check first and then construct the ResourceIdentifier

fixed with another PR: #47626