Redo how to handle stale dangling files (#7171)

foo.CORRUPTED should never be created because when
multiple sets are involved we would hash the file
to wrong a location, this PR removes the code.

But allows DeleteBucket() to work properly to delete
dangling buckets/objects. Also adds another option
to Healing where a user needs to specify `--remove`
such that all dangling objects will be deleted with
user confirmation.

pkg/madmin/heal-commands.go

@@ -30,6 +30,7 @@ import (
 type HealOpts struct {
 	Recursive bool `json:"recursive"`
 	DryRun    bool `json:"dryRun"`
+	Remove    bool `json:"remove"`
 }
 
 // HealStartSuccess - holds information about a successfully started