ExploreMetrics: Preinstall metrics drilldown app (#100094)

* feat: preinstall metrics drilldown app

* refactor: simplify

* fix: read feature toggles before plugin settings

pkg/setting/setting.go

@@ -1248,12 +1248,12 @@ func (cfg *Cfg) parseINIFile(iniFile *ini.File) error {
 	panelsSection := iniFile.Section("panels")
 	cfg.DisableSanitizeHtml = panelsSection.Key("disable_sanitize_html").MustBool(false)
 
-	if err := cfg.readPluginSettings(iniFile); err != nil {
+	// nolint:staticcheck
+	if err := cfg.readFeatureToggles(iniFile); err != nil {
 		return err
 	}
 
-	// nolint:staticcheck
-	if err := cfg.readFeatureToggles(iniFile); err != nil {
+	if err := cfg.readPluginSettings(iniFile); err != nil {
 		return err
 	}
 

pkg/setting/setting_plugins.go

@@ -58,6 +58,9 @@ func (cfg *Cfg) readPluginSettings(iniFile *ini.File) error {
 		if cfg.IsFeatureToggleEnabled("grafanaAdvisor") { // Use literal string to avoid circular dependency
 			preinstallPlugins["grafana-advisor-app"] = InstallPlugin{"grafana-advisor-app", "", ""}
 		}
+		if cfg.IsFeatureToggleEnabled("exploreMetricsUseExternalAppPlugin") { // Use literal string to avoid circular dependency
+			preinstallPlugins["grafana-metricsdrilldown-app"] = InstallPlugin{"grafana-metricsdrilldown-app", "", ""}
+		}
 		// Add the plugins defined in the configuration
 		for _, plugin := range rawInstallPlugins {
 			parts := strings.Split(plugin, "@")