Use Bash lib functions consistently in rename-env-var script

[snim2]

To test, write some nonsense:

❯ dalmatian service rename-environment-variable
[!] Error: No arguments passed
Usage: rename-environment-variable [OPTIONS]
This command can rename environment variables for a service
  -h                     - help
  -i <infrastructure>    - infrastructure name
  -s <service>           - service name
  -e <environment>       - environment name (e.g. 'staging' or 'prod')
  -k <key>               - key e.g SMTP_HOST
  -n <new-key>           - new key e.g. SMTP_PORT

You should get an error message before the usage text and the exit code of the command should be non-zero.