Go version extension commands usage don't match bash version/docs/cli help output

### Is your feature request related to a problem? Please describe

In 0.18 you use `asdf cmd []` whereas in the older version you could call `asdf []` directly.

In addition, the docs and the cli still show the old way.

I liked the old way. Is there are a reason why the `cmd` command was introduced?

### Describe the proposed solution

I have made a fork with a patch that re-introduces the old way, but also keeps the new way. Is this something work merging, or would the core rather not bring that to life.

### Describe similar `asdf` features and why they are not sufficient

none. `asdf cmd` worked as expected, it just feels more clumsy to me.

### Describe other workarounds you've considered

none

Compare the Go version's `asdf cmd []` entry point with the older Bash-style direct `asdf []` invocation, then inspect the CLI help and documentation that still show the old form. Done means the project has a clear decision on whether both forms are supported and the behavior, help output, and docs agree.

Written by the indexing model from the issue text.