`gtctl cloud` commands

[sunng87]

gtctl cloud is command line tool to manage Greptime Cloud resources. Possible commands:

• gtctl cloud login login to Greptime Cloud and persist the token
• gtctl cloud service list list existing services
• gtctl cloud service create create new services
• gtctl cloud service info <service-name> show details of service
• gtctl cloud service mysql <service-name> connect using local mysql cli
• gtctl cloud service psql <service-name> connect using local psql cli
• gtctl cloud service dashboard <service-name> open dashboard for service

[zyy17]

This issue will remain pending until the Greptime Cloud API is ready.