MM-52804 - Implement SendPushNotification plugin api method (#24273)

* add SendPushNotification plugin api method

* lint; add testing.Short bc of the sleep

* add interface and generated layers

* add fields to PluginPushNotification; generate mocks

* SendPushNotification -> SendPluginPushNotification; improved comments

* more comments; fix test

* send api.ctx

server/public/plugin/api_timer_layer_generated.go

@@ -1266,3 +1266,10 @@ func (api *apiTimerLayer) GetUploadSession(uploadID string) (*model.UploadSessio
 	api.recordTime(startTime, "GetUploadSession", _returnsB == nil)
 	return _returnsA, _returnsB
 }
+
+func (api *apiTimerLayer) SendPluginPushNotification(notification *model.PluginPushNotification) error {
+	startTime := timePkg.Now()
+	_returnsA := api.apiImpl.SendPluginPushNotification(notification)
+	api.recordTime(startTime, "SendPluginPushNotification", _returnsA == nil)
+	return _returnsA
+}