chore(client): use command's configured output (backport #22334)

[mergify]

Description

I have some external tests that invoke some of the SDK's cobra commands. Those tests often involve creating the command, calling cmd.SetOutput, executing the command, and then inspecting its output.

This change updates the client context to prefer cmd.Output if set (which should only happen in tests), falling back to stdout otherwise; so it should not change any existing client-facing behavior, but it does otherwise make command output testable.

Summary by CodeRabbit

• New Features

  • Enhanced command context to include output capabilities, improving how outputs are handled in the application.

• Tests

  • Introduced a new test to verify command output when using the updated context, ensuring reliability in output handling.

---

This is an automatic backport of pull request #22334 done by [Mergify](https://mergify.com).