Replace `window.grafanaBootData.settings.apps`

Currently, the extension dependencies between plugins are picked up from [`window.grafanaBootData.settings.apps`](https://github.com/grafana/extensionsdependencygraph-app/blob/main/src/dependency-graph-panel/utils/helpers/dataAccess.ts#L19-L41). Once Grafana is fully MT, this won't work anymore so the extension dependencies needs to be derived from somewhere else. Perhaps by calling the MT plugin meta api or by somehow exposing this through the extensions registry.