Bug: template `env` arg is not actually optional in python sdk

[andrewfulton9]

The env argument of the Template class is typed as Optional (here), however, in _internal_init, a type error is raised if env is set to None (here). Also, if I set env to [], pulumi up fails with error: graphql err: Something went wrong. Please try again later or contact support.

I would argue that env should be able to be set to None or [] without failing. However, if there is some reason it can't be, empty lists should should also be included in the type check, and it should not be typed as Optional.

Thank a lot! I really appreciate the work that has been done to allow pulumi deployments to RunPod!