bundle-diff should use juju deploy --dry-run --verbose (at least optionally)

mojo bundle-diff is very useful to gain an overview of the changes that will happen, but it doesn't show how config items will change. For example:

  Changes to deploy bundle:
  - set application options for ubuntu-mirror

With juju deploy --dry-run --verbose, it would give the following:

  - set application options for ubuntu-mirror
    setting options:
      mirror_user: "ubuntu"

which is very useful when one is dealing with a spec whose correspondence with the model is not close or otherwise in doubt.

Since this could potentially leak sensitive information, perhaps it should not be enabled by default, but it'd certainly be useful to have access to it.