Add command to get current environment name

[jongio]

When scripting it would be helpful to be able to get the current environment name without have to dig into the config.json file.

Something like az account show

[ellismg]

We already have azd show for use by tooling - maybe we can just add this to that.

[savannahostrowski]

Is this not handled by azd env list which updates as you set the use select the environment?

[jongio]

I wanted to get the name programmatically. With az cli I can use --query to get just the name, with azd I have to manually parse the results. Maybe the answer is to support --query and return json.

[savannahostrowski]

Ah I see - that make sense. Thanks for clarifying.

[savannahostrowski]

Closing in favour of #1887.