Make CLI commands atomic

**Is your feature request related to a problem? Please describe.**

I ran `amplify add auth` and then tried to add reCaptcha. I canceled the process (ctrl+c) when it asked me for my reCaptcha API key, because I didn't have one. In the end there were still new files in my `amplify` directory.

**Describe the solution you'd like**

Would be cool if the CLI just wrote files when it successfully completes a command.

**Describe alternatives you've considered**

I versioned all files with Git before running a command so I could see new files that came of a canceled command.

Reproduce `amplify add auth` and cancel at the reCaptcha API key prompt. Trace which files are written before the command completes; done means a canceled command leaves no new files in the `amplify` directory.

Written by the indexing model from the issue text.