Add Support for Cache and S3 related metrics in Prometheus endpoint (#8591)

This PR adds support below metrics

- Cache Hit Count
- Cache Miss Count
- Data served from Cache (in Bytes)
- Bytes received from AWS S3
- Bytes sent to AWS S3
- Number of requests sent to AWS S3

Fixes #8549

cmd/gateway-main.go

@@ -226,7 +226,6 @@ func StartGateway(ctx *cli.Context, gw Gateway) {
 		globalHTTPServer.Shutdown()
 		logger.FatalIf(err, "Unable to initialize gateway backend")
 	}
-
 	newObject = NewGatewayLayerWithLocker(newObject)
 
 	// Re-enable logging