Implement `shred --remove={unlink,wipesync,wipe}`

[sylvestre]

       --remove[=HOW]
              like -u but give control on HOW to delete;  See below

       Delete FILE(s) if --remove (-u) is specified.  The default is not to remove the files because it is common to operate on device files like /dev/hda, and those files usually should
       not  be  removed.  The optional HOW parameter indicates how to remove a directory entry: 'unlink' => use a standard unlink call.  'wipe' => also first obfuscate bytes in the name.
       'wipesync' => also sync each obfuscated byte to the device.  The default mode is 'wipesync', but note it can be expensive.

Tested by tests/shred/shred-remove.sh code: https://github.com/uutils/coreutils/blob/main/src/uu/shred/src/shred.rs