One shot cargo fmt

[sanket1729]

I think we should do it earlier when the diff is smaller and the project is smaller in scope. Otherwise, it becomes a big task to do it file by file as with rust-bitcoin. So far, we have had good experiences with rust-miniscript. Most rust-bitcoin developers are also in favor of using it, and I think we should get it done when the diff is relatively small and very easy to review/reproduce.

Curious what do @apoelstra, @stevenroose, and others think about this.