Source Meltano Cloud env config from dotenv file

[WillDaSilva]

Context from an internal Slack channel: https://meltano.slack.com/archives/C05LA8Q5TF1/p1693512993163689

Paraphrasing the request:

Could we have a command to convert a local .env file to cloud env set? I'm just thinking about how many times I will need to run meltano cloud env set ... for prod, and I'm not looking forward to it

This could be done with a command like meltano cloud config dotenv update that uses the file ./.env by default, or whatever paths are supplied as arguments otherwise. It would be equivalent to running meltano cloud config env set ... for each key-value pair in the dotenv file. It would not delete existing configured env values (hence update instead of set), nor would it handle env var expansion between the env and dotenv levels in the Meltano env var hierarchy, since in Meltano Cloud we use dotenv as the lowest user-configurable level, rather than env, i.e. meltano cloud config env ... and meltano cloud config dotenv ... both affect the dotenv file used in Meltano Cloud, rather than the actual env vars.