Improve API4 initialization (#18680)

* Improve API4 initialization

- Refactored openGraphDataCache to be inside app layer.
- Moved the cache instance from global variable to be inside server.
- Moved out the app instantiation from the global commands package
to be instantiated on every call. Only the server instance is passed.
- Moved InitLocal to be called from inside Init.

```release-note
NONE
```

* Remove commented line

```release-note
NONE
```

api4/system_test.go

@@ -748,7 +748,7 @@ func TestServerBusy503(t *testing.T) {
 
 func TestPushNotificationAck(t *testing.T) {
 	th := Setup(t).InitBasic()
-	api := Init(th.App, th.Server.Router)
+	api := Init(th.Server)
 	session, _ := th.App.GetSession(th.Client.AuthToken)
 	defer th.TearDown()