Orleans 7 - Enums in RequestContext are converted to int

It seems there is a regression with enums in the `RequestContext`.

Previously, I had something like this to wrap properties in the `RequestContext`

```csharp
public static OperatingMode OperatingModeFilter
{
get => RequestContext.Get(nameof(OperatingModeFilter)) as OperatingMode? ?? OperatingMode.Maintenance;
set => RequestContext.Set(nameof(OperatingModeFilter), value);
}
```

Where `OperatingMode` is an Enum

As long as I am in the same silo, the value is ok, But when the request is handled by another silo, calling `RequestContext.Get(nameof(OperatingModeFilter))` returns an int, so the safe cast `as OperatingMode?` fails and returns null