Add show command

[dimityrmirchev]

What would you like to be added:
As a user I would like to have access to information of the supported providers and rulesets that the current diki binary supports.

Add a new command called show that will serve this information. Example usages:

diki show provider // shows information for all providers

diki show provider managedk8s // shows information for "managedk8s" provider

It would be best if this command can also show which is the latest version of each ruleset for each provider.