bk artifacts list command

[lizrabuya]

This PR implements bk artifacts list command

List artifacts for a build or a job in a build.

You can pass an optional build number. If omitted, the most recent build on the current branch will be resolved.

Usage:
  bk artifacts list [build number] [flags]

Examples:
# by default, artifacts of the most recent build for the current branch is shown
$ bk artifacts list
# to list artifacts of a specific build
$ bk artifacts list 429 
# to list artifacts of a specific job in a build
$ bk artifacts list 429 --job 0193903e-ecd9-4c51-9156-0738da987e87  
# if not inside a repository or to use a specific pipeline, pass -p
$ bk artifacts list 429 -p monolith 


Flags:
  -j, --job string        List artifacts for a specific job on the given build.
  -p, --pipeline string   The pipeline to view. This can be a {pipeline slug} or in the format {org slug}/{pipeline slug}. 
                          If omitted, it will be resolved using the current directory.
  -h, --help              help for list

I have also added the artifacts UUID when listing artifacts for a build or a job to provide user a reference when we implement the bk artifacts download <artifact uuid> command.