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/filer/filer.go

@@ -9,7 +9,6 @@ import (
 	"strings"
 	"time"
 
-	"github.com/seaweedfs/seaweedfs/weed/s3api/s3_constants"
 	"github.com/seaweedfs/seaweedfs/weed/s3api/s3bucket"
 
 	"github.com/seaweedfs/seaweedfs/weed/cluster/lock_manager"
@@ -303,12 +302,8 @@ func (f *Filer) ensureParentDirectoryEntry(ctx context.Context, entry *Entry, di
 				GroupNames: entry.GroupNames,
 			},
 		}
-		// level > 3 corresponds to a path depth greater than "/buckets/<bucket_name>",
-		// ensuring we only mark subdirectories within a bucket as implicit.
 		if isUnderBuckets && level > 3 {
-			dirEntry.Extended = map[string][]byte{
-				s3_constants.ExtS3ImplicitDir: []byte("true"),
-			}
+			// Parent directories under buckets are created automatically; no additional logging.
 		}
 
 		glog.V(2).InfofCtx(ctx, "create directory: %s %v", dirPath, dirEntry.Mode)