MFC r351813: bectl(8): implement sorting for 'bectl list' output

MFC r351813: bectl(8): implement sorting for 'bectl list' output

Allow 'bectl list' to sort output by a given property name. The property
name is passed in using a command-line flag, '-c' for ascending order and
'-C' for descending order. The properties allowed to sort by are:

- name (the default output, even if '-c' or '-C' are not used)
- creation
- origin
- used
- usedds
- usedsnap
- usedrefreserv

The default output for 'bectl list' is now ascending alphabetical order of
BE name.

To sort by creation time from earliest to latest, the command would be
'bectl list -c creation'