MM-12849 Moving all non request scoped items to Server struct (#9806)

* Moving goroutine pool

* Auto refactor

* Moving plugins.

* Auto refactor

* Moving fields to server

* Auto refactor

* Removing siteurl duplication.

* Moving reset of app fields

* Auto refactor

* Formatting

* Moving niling of Server to after last use

* Fixing unit tests.

app/config_test.go

@@ -35,11 +35,12 @@ func TestLoadConfig(t *testing.T) {
 	require.Nil(t, err)
 	tempConfig.Close()
 
-	a := App{}
+	a := App{
+		Srv: &Server{},
+	}
 	appErr := a.LoadConfig(tempConfig.Name())
 	require.Nil(t, appErr)
 
-	assert.Equal(t, "http://localhost:8065", a.siteURL)
 	assert.Equal(t, "http://localhost:8065", *a.GetConfig().ServiceSettings.SiteURL)
 }