Better Wrangler config diff

[penalosa]

Describe the solution

For internal context, see https://wiki.cfdata.org/pages/viewpage.action?pageId=1187489699

When using both Wrangler and the dash to update a Worker, it's easy to get into situations where there's a potential conflict. Today, Wrangler warns about those cases in interactive mode, but it doesn't provide much information about why there's a diff.

We should:

1. Display a rich diff of what the actual config differences are (instead of just a warning that differences exist), so that the user has the opportunity to review. We can re-use the init --from-dash codepaths here that can already construct a representation of a Worker's remote state as Wrangler config.
2. If the user chooses not to deploy, we should offer to update their local wrangler.json with the remote changes (this will only work for json config files).
3. We should implement an opt-in "strict-mode" that fails deploys with config conflicts in non-interactice mode if a --force flag isn't provided. i.e. a user would use wrangler deploy --strict as their deploy command.