gsutil rm => remove by owner

`gsutil rm -r` will fail with `CommandException: 1 files/objects could not be removed.` if the user does not have permissions for some of the files in the folder.

It would greatly help to add a flag for skipping the removal of files in which the user lacks permissions.

Start with the gsutil rm -r command and trace how it handles permission failures while removing files or objects. Determine where an option to skip inaccessible items belongs, then verify that recursive removal continues successfully and still reports or handles other failures appropriately.

Written by the indexing model from the issue text.