Simplify dbos-cloud app deploy

[qianl15]

This PR aims to reduce DBOS Cloud app deploy to a single command.

• First, check if the app is registered or not. If so, proceed to the normal deploy (this PR is fully backward compatible).
• If the app is not registered, then select a database server to use for this app.
  • List all database servers for the current user.
  • If the user doesn't have any database, then prompt to provision one.
  • If the user has more than one database servers, then prompt to choose one.
  • If the user has only one database server, then use it.
• Finally, register the app and deploy normally.

Discussion:

• Currently, it uses a default PG role name dbosapp_default and a generated password. Do we want user input for those?