unified-storage: setup ring to shard requests (#103783)

* Updates the instrumentation_server service to use mux instead of the builtin router, and have it store the router in the module server: this is so we can register the /ring endpoint to check the status of the ring
* Create a new Ring service that depends on the instrumentation server and declares it as a dependency for the storage server
* Create standalone MemberlistKV service for Ring service to use
* Update the storage server Search and GetStats handler to distribute requests if applicable

pkg/server/instrumentation_service_test.go

@@ -18,7 +18,12 @@ import (
 func TestRunInstrumentationService(t *testing.T) {
 	cfg := setting.NewCfg()
 	cfg.HTTPPort = "3001"
-	s, err := NewInstrumentationService(log.New("test-logger"), cfg, prometheus.DefaultGatherer)
+	ms := ModuleServer{
+		log:          log.New("test-logger"),
+		cfg:          cfg,
+		promGatherer: prometheus.DefaultGatherer,
+	}
+	s, err := ms.initInstrumentationServer()
 	require.NoError(t, err)
 
 	ctx, cancel := context.WithTimeout(context.Background(), 300*time.Second)