The prometheus metrics refractoring (#8003)

The measures are consolidated to the following metrics

- `disk_storage_used` : Disk space used by the disk.
- `disk_storage_available`: Available disk space left on the disk.
- `disk_storage_total`: Total disk space on the disk.
- `disks_offline`: Total number of offline disks in current MinIO instance.
- `disks_total`: Total number of disks in current MinIO instance.
- `s3_requests_total`: Total number of s3 requests in current MinIO instance.
- `s3_errors_total`: Total number of errors in s3 requests in current MinIO instance.
- `s3_requests_current`: Total number of active s3 requests in current MinIO instance.
- `internode_rx_bytes_total`: Total number of internode bytes received by current MinIO server instance.
- `internode_tx_bytes_total`: Total number of bytes sent to the other nodes by current MinIO server instance.
- `s3_rx_bytes_total`: Total number of s3 bytes received by current MinIO server instance.
- `s3_tx_bytes_total`: Total number of s3 bytes sent by current MinIO server instance.
- `minio_version_info`: Current MinIO version with commit-id.
- `s3_ttfb_seconds_bucket`: Histogram that holds the latency information of the requests.

And this PR also modifies the current StorageInfo queries

- Decouples StorageInfo from ServerInfo .
- StorageInfo is enhanced to give endpoint information.

NOTE: ADMIN API VERSION IS BUMPED UP IN THIS PR

Fixes #7873

browser/app/js/browser/StorageInfo.js

@@ -26,6 +26,7 @@ export class StorageInfo extends React.Component {
   }
   render() {
     const { used } = this.props.storageInfo
+    var totalUsed = used.reduce((v1, v2) => v1 + v2, 0)
     return (
       <div className="feh-used">
         <div className="fehu-chart">
@@ -34,7 +35,7 @@ export class StorageInfo extends React.Component {
         <ul>
           <li>
             <span>Used: </span>
-            {humanize.filesize(used)}
+            {humanize.filesize(totalUsed)}
           </li>
         </ul>
       </div>
@@ -54,4 +55,7 @@ const mapDispatchToProps = dispatch => {
   }
 }
 
-export default connect(mapStateToProps, mapDispatchToProps)(StorageInfo)
+export default connect(
+  mapStateToProps,
+  mapDispatchToProps
+)(StorageInfo)