Fix for "env" param in cmd state/module

This pull request fixes the usage of the ``env`` param in the cmd state and module. In both, ``env`` is meant to define the OS environment (i.e. environment variables), but the state compiler assigns this value to the "magic" dunder ``__env__``. This effectively breaks these states.

This, along with https://github.com/saltstack/salt/pull/11397, provides a fix for https://github.com/saltstack/salt/issues/11189.