secrets ls should be able to operate on multiple paths #321

Specification

In Unix, the ls command is able to list out the contents of each provided argument. This currently is not the case with the secrets ls command.

This needs to be updated to align with Unix expectations.

[aryanj@matrix-34xx:~]$ ls dir1
file1  file2

[aryanj@matrix-34xx:~]$ ls dir1 dir2
dir1:
file1 file2

dir2:
another_file  one_more_file

Additional context

Tasks

1. Implement multiple vault listing support
2. Write tests (use fastcheck where possible)