More flexible mix & match options for message stores in the same application

[jeremydmiller]

Started as "Ancillary Marten stores don't necessarily use the correct message database in inbox/outbox operations"

This is really becoming a "make Wolverine awesome for modular monoliths" by making it possible to more readily mix and match different message stores and durability agents within the same application. So:

• Readily use separate Marten stores, but "know" how many unique message store databases there are and make sure you're always using the right one
• Mix & match Marten & EF Core against the same postgresql database
• Use completely separate Marten stores or EF Core DbContext in the same app pointed at different logical databases
• Mix & match RavenDb & Postgresql & Sql Server in the same app
• Accomodate multi-tenancy too

The envelopes are going to the correct database schema, but the DurableReceiver and durable sending agents aren't using the correct databases.

Only really an issue for local queues where messages are sent as part of a message using the ancillary store

[jeremydmiller]

Use this test in the code to bring out the problem:

    [Fact]
    public async Task try_to_use_the_session_transactional_middleware_end_to_end_through_a_queue()
    {
        var message = new SpawnPlayerMessage(Guid.NewGuid().ToString());
        var tracked = await theHost.InvokeMessageAndWaitAsync(message, timeoutInMilliseconds:60000);
        var envelopeId = tracked.Executed.SingleEnvelope<PlayerMessage>().Id;
    
        var store = theHost.DocumentStore<IPlayerStore>();
        using var session = store.QuerySession();
        var player = await session.LoadAsync<Player>(message.Id);
    
        player.ShouldNotBeNull();
    
        var runtime = theHost.GetRuntime();
        var messageStore = runtime.AncillaryStores.OfType<IAncillaryMessageStore<IPlayerStore>>().Single();
        var envelope = (await messageStore.Admin.AllIncomingAsync()).Single(x => x.Id == envelopeId);
        envelope.Status.ShouldBe(EnvelopeStatus.Handled);
        envelope.OwnerId.ShouldBe(TransportConstants.AnyNode);
    }

Basic issue is that the ancillary store is being more or less ignored and still using the main postgres message store. No big deal if you're all on the same database, but still.