ns/nim: Stub eShop related calls (#1420)

* ns/nim: Stub eShop related calls

As we aren't able to process purchase on the eShop throught the emulator, I have:
- Stub IPurchaseEventManager::SetDefaultDeliveryTarget (with RE check).
- Implement IPurchaseEventManager::GetPurchasedEventReadableHandle (with RE check).

As we can't do any eShop async call throught the emulator, I have:
- Stub IShopServiceAccessServerInterface::CreateServerInterface
- Stub IShopServiceAccessServer::CreateAccessorInterface
- Stub IShopServiceAccessor::IShopServiceAsync

Close #1084 and #1322

* fix handle copy

* Fix align

* Fix readonly event

Ryujinx.HLE/HOS/Services/Nim/IShopServiceAccessor.cs

@@ -0,0 +1,37 @@
+using Ryujinx.Common.Logging;
+using Ryujinx.HLE.HOS.Ipc;
+using Ryujinx.HLE.HOS.Kernel.Common;
+using Ryujinx.HLE.HOS.Kernel.Threading;
+using Ryujinx.HLE.HOS.Services.Nim.ShopServiceAccessServerInterface.ShopServiceAccessServer.ShopServiceAccessor;
+using System;
+
+namespace Ryujinx.HLE.HOS.Services.Nim.ShopServiceAccessServerInterface.ShopServiceAccessServer
+{
+    class IShopServiceAccessor : IpcService
+    {
+        private readonly KEvent _event;
+
+        public IShopServiceAccessor(Horizon system)
+        {
+            _event = new KEvent(system.KernelContext);
+        }
+
+        [Command(0)]
+        // CreateAsyncInterface(u64) -> (handle<copy>, object<nn::ec::IShopServiceAsync>)
+        public ResultCode CreateAsyncInterface(ServiceCtx context)
+        {
+            MakeObject(context, new IShopServiceAsync());
+
+            if (context.Process.HandleTable.GenerateHandle(_event.ReadableEvent, out int handle) != KernelResult.Success)
+            {
+                throw new InvalidOperationException("Out of handles!");
+            }
+
+            context.Response.HandleDesc = IpcHandleDesc.MakeCopy(handle);
+
+            Logger.PrintStub(LogClass.ServiceNim);
+
+            return ResultCode.Success;
+        }
+    }
+}