Add support for sending health check to datasource plugins. (#22771)

closes #21519
ref grafana/grafana-plugin-sdk-go#93

pkg/api/http_server.go

@@ -73,6 +73,7 @@ type HTTPServer struct {
 	Login                *login.LoginService      `inject:""`
 	License              models.Licensing         `inject:""`
 	BackendPluginManager backendplugin.Manager    `inject:""`
+	PluginManager        *plugins.PluginManager   `inject:""`
 }
 
 func (hs *HTTPServer) Init() error {