Print a list of storage (and possibly converter) plugins + description

[Martin-Idel-SI]

Currently, there is no way to know which converter and storage plugins are installed. This is annoying for storage plugins as rosbag_v2 as you need to know its name to play an old bagfile.

Provide a way to get a list of all installed plugins via command line.

I see a few options here:

• Try to provide autocompletion on -s (would be the nicest solution in my eyes)
• Add an option like --list-storage-plugins for ros2 bag play/record
• New verb for ros2 bag

[cottsay]

@Karsten1987, do you have any thoughts on the three approaches listed here?