Akka.FSharp: need to re-enable discriminated union (DU) serialization tests

[Aaronontheweb]

Version Information
Version of Akka.NET? v1.4.23
Which Akka.NET Modules? Akka.FSharp

Describe the bug
https://stackoverflow.com/questions/68741561/akka-unable-to-send-discriminated-unions-as-messages-in-f#comment121522181_68741561 - looks like default DU serialization isn't working with Newtonsoft.Json per this user's report.

As it so happens, our DU serialization tests are out of date and commented out:

akka.net/src/core/Akka.FSharp.Tests/ApiTests.fs

Lines 41 to 76 in d146387

	//
	//[<Fact>]
	//let ``can serialize and deserialize discriminated unions over remote nodes using wire serializer`` () =
	// let remoteConfig port =
	// sprintf """
	// akka {
	// actor {
	// ask-timeout = 5s
	// provider = "Akka.Remote.RemoteActorRefProvider, Akka.Remote"
	// serialization-bindings {
	// "System.Object" = wire
	// }
	// }
	// remote {
	// dot-netty.tcp {
	// port = %i
	// hostname = localhost
	// }
	// }
	// }
	// """ port
	// |> Configuration.parse
	//
	// use server = System.create "server-system" (remoteConfig 9911)
	// use client = System.create "client-system" (remoteConfig 0)
	//
	// let aref =
	// spawne client "a-1" <@ actorOf2 (fun mailbox msg ->
	// match msg with
	// | C("a-11", B(11, "a-12")) -> mailbox.Sender() <! msg
	// | _ -> mailbox.Unhandled msg) @>
	// [SpawnOption.Deploy (Deploy(RemoteScope (Address.Parse "akka.tcp://server-system@localhost:9911")))]
	// let msg = C("a-11", B(11, "a-12"))
	// let response = aref <? msg |> Async.RunSynchronously
	// response
	// |> equals msg

I think a lot of this stems from the Akka.NET v1.3 push and the fact that F# lagged behind a bit on .NET Core support at the time. Now that everything is pretty reliable there for the most part we should reintroduce these tests as part of our suite.

Actual behavior
Not sure, but it looks like the DU content is lost in translation.

Expected behavior
DUs should be serializable via:

• Newtonsoft.Json
• Hyperion

With all of its contents correctly preserved.

[Aaronontheweb]

Whoops, not done yet. Just had to re-enable some F# platform support in the Akka.FSharp.Tests project.