Usage propagation leads to API change of DiskRestorePointData

[pshao25]

This is to track the known issue for the API change of DiskRestorePointData when we do the validation of Compute migrating to TypeSpec. The change is DiskRestorePointData is changed from output to roundtrip, which leads to new setter added to the properties of DiskRestorePointData.

The root cause is:
Previously, DiskRestorePoint extends ProxyOnlyResource, and itself is output only. Therefore, DiskRestorePointData is output.
But now, DiskRestorePoint extends common ProxyResource, which is shared across all the other resources that are roundtrip. Therefore, the roundtrip usage is propagated to DiskRestorePoint and DiskRestorePointData becomes roundtrip.

We won't have this issue for TypeSpec input. It only exists for swagger input. So we won't take action now.