Describe the bug
When retrieving an IGenericResource instance from genericResources.ListByResourceGroupAsync ApiVersion property is null.

To Reproduce
The resource already exists and when showing ARM template in Azure ApiVersion is filled.

var resources = await genericResources.ListByResourceGroupAsync(Config.ResourceGroup);
foreach (var resource in resources)
{
    // resource.ApiVersion is always null
    await resource.Update().WithApiVersion(resource.ApiVersion).WithTags(new DefaultTags()).ApplyAsync();
}

Expected behavior
IGenericResource.ApiVersion should be filled with the correct ApiVersion that was used when the resource was created or updated.

Setup (please complete the following information):

• Microsoft.Azure.Management.Fluent 1.31.0
• Microsoft.Azure.Management.ResourceManager.Fluent 1.31.0