[anodized-fmt] feat: run `rustfmt` before spec formatting

[mkovaxx]

Currently we expect the user to first run rustfmt, then run anodized-fmt.

After this change, they'd only need to run anodized-fmt.

[chammika]

What about adding a --with-rustfmt flag as an opt-in?
That way people who want the single-command workflow
can use anodized-fmt --with-rustfmt, while the default stays minimal and focused on spec formatting only.

[mkovaxx]

Good point! We should start with that, and make it the default once it works reliably! :)