Extend k6 with subcommands

[szkiba]

What

As a k6 extension developer, I would like to extend the k6 CLI functionality with subcommands.

In addition, CLI tools are sometimes being developed for k6 JavaScript/Output extensions.
I would like to embed these tools together with the extension into k6.

Why

The best user experience for k6-related tools is embedding them as subcommands.

Embedding into k6 simplifies the distribution and use of these tools.

How

In addition to the JavaScript and Output k6 extension types, a Command extension type should be introduced.

The Command extension would be suitable for creating a k6 subcommand.

Related

An earlier attempt at this topic:

• feat: command extension type support #3293

It is advisable to take these into account during planning/implementation:

• Provide access to k6 CLI definition #4013
• Generate k6 CLI documentation from the k6 command definition #4014