Add Drilldown Plugins to Default Grafana Distribution

<!-- Please only use this template for submitting feature requests --> **Why is this needed**: Drilldown functionality is enabled by default in Grafana, but the required drilldown plugins are not included in the default distribution. Instead, Grafana attempts to download these plugins from the internet during runtime. This behavior creates significant challenges for users operating in closed or restricted network environments, where external downloads are not possible [Add a description of the problem the feature is trying to solve.] **What would you like to be added**: To address this issue, the drilldown plugins should be included in the default Grafana distribution packages (e.g., Docker images, .deb packages, etc.). By bundling these plugins, Grafana would provide a more seamless experience for users, especially those in environments with limited or no internet access. This change would reduce the additional workload for administrators who currently need to manually download and configure these plugins. [Add a brief description of what the feature or enhancement should do.] **Who is this feature for?** This feature would benefit all Grafana users, particularly those working in closed network environments or organizations with strict security policies that restrict external downloads. [Add information on what kind of user the feature is for.] Check in last version of Grafana (Docker image, 12.0.2-ubuntu) Error logs in Grafana: ``` logger=plugin.backgroundinstaller t=2025-06-18T07:40:21.454619082Z level=error msg="Failed to install plugin" pluginId=grafana-exploretraces-app version= error="Get \"https://grafana.com/api/plugins/grafana-exploretraces-app/versions\": dial tcp 34.120.177.193:443: connect: connection refused" logger=plugin.backgroundinstaller t=2025-06-18T07:40:21.454661461Z level=info msg="Installing plugin" pluginId=grafana-metricsdrilldown-app version= logger=grafana.update.checker t=2025-06-18T07:40:21.455236484Z level=error msg="Update check faile…