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/api-response.go

@@ -526,7 +526,7 @@ func generateListObjectsV2Response(bucket, prefix, token, nextToken, startAfter,
 		if metadata {
 			content.UserMetadata = make(StringMap)
 			for k, v := range CleanMinioInternalMetadataKeys(object.UserDefined) {
-				if hasPrefix(k, ReservedMetadataPrefix) {
+				if HasPrefix(k, ReservedMetadataPrefix) {
 					// Do not need to send any internal metadata
 					// values to client.
 					continue