fix(roles/grafana_grizzly): move dashboards back into their folder on Grafana 13.1+

[markuslf]

On icinga-demo (Grafana 13.2.2), the graphs embedded in IcingaWeb2 failed with "Failed to load dashboard 403" for 18 of the Monitoring Plugins dashboards, among them memory-usage, ping and cpu-usage.

Grafana 13.1 routes /api/dashboards/db into the Kubernetes save path, which sets the folder from folderUid only (saveDashboardViaK8s() in pkg/api/dashboard.go, grafana/grafana#122027). grizzly sends folderId, so every dashboard it adds or updates lands in the root. A dashboard moved there loses the viewer permission it inherited from the folder, while dashboards created in the root get their own; the anonymous viewer that IcingaWeb2 embeds Grafana with then gets 403. No grizzly release sends folderUid.

Changes

• roles/shared, grafana-move-dashboards-into-folders.yml: takes the dashboards and their folders, reads the current folder of every dashboard with a single /api/search, and saves only the misfiled ones again with folderUid. That puts them back and restores the permission. Dashboards Grafana does not know, and those whose resource names general (the root in grizzly), are left alone.
• roles/grafana_grizzly, roles/monitoring_plugins_grafana_dashboards: call it after grr apply, with the Dashboard resources parsed from the applied files on the controller.
• READMEs ("How the Role Behaves") and CHANGELOG.

Stopgap until the switch to gcx (Linuxfabrik/monitoring-plugins#1062).

Tests

• icinga-demo, setup_icinga2_master --tags monitoring_plugins_grafana_dashboards: with swap-usage changed in Grafana beforehand, grr reported Dashboard.swap-usage updated and filed it in the root, the new task moved it back. Afterwards no Linuxfabrik dashboard was in the root, swap-usage answered the anonymous viewer with 200 and carried the content grizzly applied.
• Same run without drift: nothing saved, --check reads only.
• Parsing: 188 dashboards with a folder from the Monitoring Plugins; the resources of 001-p-app91 (kind: Dashboard quoted and unquoted, folder: general) are recognised and skipped.
• ansible-lint on the changed roles: only the four existing findings outside these lines. No Molecule scenario exists for Grafana.