ListObjects Metadata Caching (#10648)

Design: https://gist.github.com/klauspost/025c09b48ed4a1293c917cecfabdf21c

Gist of improvements:

* Cross-server caching and listing will use the same data across servers and requests.
* Lists can be arbitrarily resumed at a constant speed.
* Metadata for all files scanned is stored for streaming retrieval.
* The existing bloom filters controlled by the crawler is used for validating caches.
* Concurrent requests for the same data (or parts of it) will not spawn additional walkers.
* Listing a subdirectory of an existing recursive cache will use the cache.
* All listing operations are fully streamable so the number of objects in a bucket no 
  longer dictates the amount of memory.
* Listings can be handled by any server within the cluster.
* Caches are cleaned up when out of date or superseded by a more recent one.

cmd/fs-v1.go

@@ -402,6 +402,7 @@ func (fs *FSObjects) MakeBucketWithLocation(ctx context.Context, bucket string,
 		return BucketNameInvalid{Bucket: bucket}
 	}
 
+	defer ObjectPathUpdated(bucket + slashSeparator)
 	atomic.AddInt64(&fs.activeIOCount, 1)
 	defer func() {
 		atomic.AddInt64(&fs.activeIOCount, -1)