Investigate click and typer

[gctucker]

The current kci command line tool is based on the same code as in the legacy tools kci_build, kci_test etc. As part of needing a redesign, it's worth considering alternative packages such as click and typer (which is based on click).

Investigating whether we can use them and comparing them can be done by implementing the basic support for loading settings values from TOML for the current command, looking up TOML settings groups based on a config name (e.g. to find an API token for a particular API instance config), implementing some dummy nested commands as well as a real whoami command as a proof-of-concept.

• Initial investigation of click [RFC] kci-click: add kci PoC using Click #2111
• Initial investigation of typer [RFC] kci-typer: add kci PoC using Typer #2112
• Summary and comparison
• Discussed with users and community
• Follow-up plan described on GitHub kci command line tool rework #2125