Add ExecutionID to slack.MessageArgs

[alexandrchumakin]

It will be really useful if we could send a link to testkube dashboard in a slack notification, so we need to extend MessageArgs with ExecutionID and populate it with ExecutionID: execution.Id, at composeTestsuiteMessage and composeTestMessage methods. Then we can extend slack notification with a section like:

{
	"type": "section",
	"text": {
		"type": "mrkdwn",
		"text": "To open execution in dashboard go to https://{host}/tests/executions/{{ .TestName }}/execution/{{ .ExecutionID }} \n"
	}
}

[vsukhin]

hey @alexandrchumakin Thank you for your suggestion. Looks like a good idea. In general, we should have somehere a github issue regarding usage of templates for slack notification. So, it will also help and with other similar improvements. Feel free to open a github issue and we will add it to planned tasks or might be you want to contribute :)