Switch empty-folder cleanup to bucket policy (#8292)

* Fix Spark _temporary cleanup and add issue #8285 regression test

* Generalize empty folder cleanup for Spark temp artifacts

* Revert synchronous folder pruning and add cleanup diagnostics

* Add actionable empty-folder cleanup diagnostics

* Fix Spark temp marker cleanup in async folder cleaner

* Fix Spark temp cleanup with implicit directory markers

* Keep explicit directory markers non-implicit

* logging

* more logs

* Switch empty-folder cleanup to bucket policy

* Seaweed-X-Amz-Allow-Empty-Folders

* less logs

* go vet

* less logs

* refactoring

weed/command/filer_remote_gateway_buckets.go

@@ -390,11 +390,10 @@ func (option *RemoteGatewayOptions) detectBucketInfo(actualDir string) (bucket u
 }
 
 func extractBucketPath(bucketsDir, dir string) (util.FullPath, bool) {
-	if !strings.HasPrefix(dir, bucketsDir+"/") {
-		return "", false
+	if bucketPath, ok := util.ExtractBucketPath(bucketsDir, dir, false); ok {
+		return util.FullPath(bucketPath), true
 	}
-	parts := strings.SplitN(dir[len(bucketsDir)+1:], "/", 2)
-	return util.FullPath(bucketsDir).Child(parts[0]), true
+	return "", false
 }
 
 func (option *RemoteGatewayOptions) collectRemoteStorageConf() (err error) {