@wordpress/env: Add a debug mode

[noisysocks]

It would be helpful for debugging issues with wp-env if wp-env supported a verbose or debugging mode.

To do this we can add a --debug flag to wp-env start which, if specified:

• Outputs the computed config object (the result of initConfig()).
• Outputs the generated docker-compose.yml file.
• Outputs the docker-compose commands that are ran.
  • Outputs the STDOUT (and STDERR, though we do this already) of these commands.
• Outputs the git commands that are ran.
  • Outputs the STDOUT (and STDERR) of these commands.

Optionally, we could make it so that wp-env outputs this log when an error is encountered even if --debug was not specified.

cc. @epiqueras @noahtallen