Request: support remoteBuild: "prefer" or similar

[pamelafox]

We are currently experiencing an issue with our templates that use remoteBuild: true, because free trial subscriptions cannot use that ACR functionality. Instead of folks having to know how to delete that line, what if we had "remoteBuild: prefer"? Then it could use ACR if it works, and if it gets that exception, fallback to a docker build.

[weikanglim]

In discussion today, the team is thinking to add the fallback behavior by default, so remoteBuild: true will revert back to local docker builds if any exception occurs while building remotely.

[pamelafox]

That sounds good!