Refactors GetPluginDashboards/LoadPluginDashboard by moving database
interaction from plugin management to the plugindashboards service.
Fixes#44553
Co-authored-by: Will Browne <wbrowne@users.noreply.github.com>
Moves/refactor Grafana specific functionality related to plugin dashboards
out to specific services for importing dashboards and keep app plugin dashboards
up-to-date.
Fixes#44257