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/tests/testinfra/testinfra.go

@@ -104,7 +104,7 @@ func StartGrafanaEnv(t *testing.T, grafDir, cfgPath string) (string, *server.Tes
 	var storage sql.UnifiedStorageGrpcService
 	if runstore {
 		storage, err = sql.ProvideUnifiedStorageGrpcService(env.Cfg, env.FeatureToggles, env.SQLStore,
-			env.Cfg.Logger, prometheus.NewPedanticRegistry(), nil, nil, nil)
+			env.Cfg.Logger, prometheus.NewPedanticRegistry(), nil, nil, nil, nil)
 		require.NoError(t, err)
 		ctx := context.Background()
 		err = storage.StartAsync(ctx)