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/plugin_hooks_test.go

@@ -44,7 +44,7 @@ func SetAppEnvironmentWithPlugins(t *testing.T, pluginCode []string, app *App, a
 	env, err := plugin.NewEnvironment(apiFunc, pluginDir, webappPluginDir, app.Log)
 	require.NoError(t, err)
 
-	app.Plugins = env
+	app.Srv.Plugins = env
 	pluginIds := []string{}
 	activationErrors := []error{}
 	for _, code := range pluginCode {