fix(cli): exit code 1 on unknown commands, sub-commands and flags

[vvagaytsev]

What this PR does / why we need it:
This PR brings strict consistency into Garden command exit codes and fixes the possible CI problems like the ones we got in #4868.

Which issue(s) this PR fixes:

Fixes #4911

Special notes for your reviewer:
This PR has been done in TDD mode :)
The test specs were written first.

To be back-ported to 0.12.

TODOs (to be addressed in a separate PR):

• ensure the error message is always printed on unrecognized flag
• ensure the error message is always printed on unrecognized command or sub-command

[stefreak]

Great work! I have one minor comment on a comment.

I like the tests a lot ❤️

[stefreak]

One comment on the plan to backport this to 0.12: Do we have to do that? I think it might not be important enough to justify the effort (But I might be wrong, you might have good reasons).

[vvagaytsev]

One comment on the plan to backport this to 0.12: Do we have to do that? I think it might not be important enough to justify the effort (But I might be wrong, you might have good reasons).

It's not super critical, but it might be better to align the exit code behavior between 0.12 and 0.13. The back-port should be a big effort. We're going to do the next 0.12 release soon, so we can include this fix too.