[CLI] Feature requests: List env vars & Different exports per env?

[corinagum]

• Currently in the CLI you can use spark env list to list the environments, but right now the only way to check the values inside the environment is to export it to env file
• Export different .env files based on environment? if you do spark export dev and then spark export prod the .env file will be overwritten. Not sure how intentional that is or if others would find this valuable