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* Caches are cleaned up when out of date or superseded by a more recent one.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/erasure-bucket.go

@@ -158,6 +158,7 @@ func deleteDanglingBucket(ctx context.Context, storageDisks []StorageAPI, dErrs
 // DeleteBucket - deletes a bucket.
 func (er erasureObjects) DeleteBucket(ctx context.Context, bucket string, forceDelete bool) error {
 	// Collect if all disks report volume not found.
+	defer ObjectPathUpdated(bucket + slashSeparator)
 	storageDisks := er.getDisks()
 
 	g := errgroup.WithNErrs(len(storageDisks))