[feature request]: allow iterating over object in comprension (like dict comprehension in python)

[bendavis78]

It would be useful to be able to do something like dict comprehensions in python, eg: for key, value in obj

A use-case would be when defining environment variables for a kubernetes container like so:

{
  env:: {
    FOO: 'foo',
    BAR: 'bar',
    BAZ: 'baz'
  },
  containerEnv: [{name: k, value: v} for k, v in $.env]
}

->

{"containerEnv": [
  {"name": "FOO", "value": "foo"},
  {"name": "BAR", "value": "bar"},
  {"name": "BAZ", "value": "baz"}
]}

[sbarzowski]

You can do this currently with std.objectFields/std.objectFieldsAll. See also: #543.

Maybe we could add a shorthand syntax for that like in your example.