[Feature Request] Fail if provided `--env`/`TEMPORAL_ENV` is unknown

[cretz]

Describe the solution you'd like

We think we want to fail users if they provide an env that isn't there. Discussion points:

• What did pre-0.12.0 versions do?
• Do we want to fail or warn? We think we want to fail but could be big compat break from above bullet if we never did before.
• What if the env exists but is empty? Should we start removing empty envs from the config when their last value is removed?
• Make clear in the error what is invalid just in case it's some leftover TEMPORAL_ENV env var that has a bad value

[josh-berry]

We should make sure not to break temporal env commands when we do this, because temporal env set --env ... can be used to create new environments.

[Sushisource]

Confirmed that the old CLI does break on unknown envs, so will be fixing.