Provisioned dashboard folder remains when source-folders has been removed, cluttering the ui

### What happened? Problem Provisioning dashboards with folders from filestructure leaves folders behind when the folders are deleted and not anymore there. This creates the need of manual interaction such as deleting the left-over folders manually or cleaning entire dashboard-database. To Reproduce, we use a dedicated service with messaging that creates an removes dashboards within folders for multiple applications. In other words this is basically an iac approach. What we observed: We create a folder "anton" and a json dashboard "anton/banana-dashboard.json": Full pathname: /var/lib/dashboards/anton/banana-dashboard.json We create another folder "mike" and a json dashboard "mike/kiwi-dashboard.json" Grafana creates a folder anton and mike with the expected dashboards. So far all seems good. Then after some time we delete the folder anton its files. We would expect the dashboard and its folder is deleted since the folder was only added by provisioning logic. However here the folder remains in the ui and is responsible for cluttering old content. Our only possible workaround is to completely delete the internal database content and let the provisioning add the current state. Is this behavior expected and works as designed or a bug? ### What did you expect to happen? The folder schould be removed in the ui as soon as the physical folder from provisioning is removed. The folder's lifecycle seems only cover the creation but not the deletion. ### Did this work before? No that was a problem from start of provisioning as far as I inverstigated. ### How do we reproduce it? To reproduce there is a set of configmaps / statefulset for openshift / kubernetes where you could try out the same within a persistent volume claim and follow the notes.txt instructions to reproduce leaving the folder "hello-my-dear" behind. 1. Sample procedure to create one folder within provisioned dashboards: ` cd /var/lib/dashboards/ mkdir hello-my-dear cd hello-my-dear/ cp ../../dummy-dashboards/an…