[FEATURE REQ] Implement SystemData for ProxyResource

### API Spec link

https://github.com/Azure/azure-rest-api-specs/pull/29184

### API Spec version

2023-09-01-preview

### Please describe the feature.

We need to latest version of `ProxyResource` for the rest-api-specs, i.e. v5

But it supports `SystemData` which our control plane does not support. This is Workitem to request support for that.