account: Implement IManagerForApplication calls and IAsyncContext (#1466)

* account: Implement IManagerForApplication calls and IAsyncContext

This implement:
- IManagerForApplication::EnsureIdTokenCacheAsync (accordingly to RE) but the Async task is stubbed.
- IAsyncContext interface (accordingly to RE).
- IManagerForApplication::LoadIdTokenCache (checked with RE, and stubbed).

I've tried some games but now they needs some `sfdnsres` calls, some other boots and crashes with other issues.
Maybe we should disable the connection somewhere to lets the game think we are offline. I have done many attempts, without success, but since the code is here now, it's better than nothing.

(I've cleaned up `using` of IGeneralService too)

Closes #629 and closes #630

* change AccountId

* Fix gdkchan's comments

* use CompletedTask

Ryujinx.HLE/HOS/Services/Account/Acc/AsyncContext/AsyncExecution.cs

@@ -0,0 +1,56 @@
+using Ryujinx.Common.Logging;
+using Ryujinx.HLE.HOS.Kernel.Threading;
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Ryujinx.HLE.HOS.Services.Account.Acc.AsyncContext
+{
+    class AsyncExecution
+    {
+        private readonly CancellationTokenSource _tokenSource;
+        private readonly CancellationToken       _token;
+
+        public KEvent SystemEvent   { get; }
+        public bool   IsInitialized { get; private set; }
+        public bool   IsRunning     { get; private set; }
+
+        public AsyncExecution(KEvent asyncEvent)
+        {
+            SystemEvent = asyncEvent;
+
+            _tokenSource = new CancellationTokenSource();
+            _token       = _tokenSource.Token;
+        }
+
+        public void Initialize(int timeout, Func<CancellationToken, Task> taskAsync)
+        {
+            Task.Run(async () =>
+            {
+                IsRunning = true;
+
+                _tokenSource.CancelAfter(timeout);
+
+                try
+                {
+                    await taskAsync(_token);
+                }
+                catch (Exception ex)
+                {
+                    Logger.Warning?.Print(LogClass.ServiceAcc, $"Exception: {ex.Message}");
+                }
+
+                SystemEvent.ReadableEvent.Signal();
+
+                IsRunning = false;
+            }, _token);
+
+            IsInitialized = true;
+        }
+
+        public void Cancel()
+        {
+            _tokenSource.Cancel();
+        }
+    }
+}