Tesla: remove client ID

[andig]

With #17501 we're relying on users to supply their own Tesla Client ID. They can use https://www.myteslamate.com/tesla-api-application-registration/ which provides this free of charge. As a benefit, they get 10$ free requests per month for personal use.

To complete this transition by end of January, we should remove the Tesla Client ID from the build process and hint users accordingly.

This prepares for evcc Tesla client only providing command proxy. We can then better understand, what cost and efforts are involved with running the command proxy in future.