Match System.Reactive namespaces #9
Description
Currently, we provide all types in the top-level System namespace, which makes consumption straightforward but which isn't 100% compatible with System.Reactive.
For example, Rx uses System.Reactive.Linq for the OfType/Where/Select extension methods, System.Reactive.Subjects and System.Reactive.Disposables.
Even though using separate namespaces for just one or two types (in our case) would seem unnecessary, by not using the same namespaces as System.Reactive, this package is not a simple drop-in replacement (neither can it be replaced by just switching to the full Rx package), since compilation errors will need fixing from the namespace mismatches.
We should instead be 100% compatible so that switching packages is all that's needed.