Enable auto formatting the imports with `rustfmt` when it is stable

### Which components does the task require to be changed? (think hard pls)

snforge, sncast

### Description

There's a feature in `rustfmt` which enables auto-formatting the imports, but it's only available in nightly versions
https://github.com/rust-lang/rustfmt/issues/4991

However, we use stable versions of `rust` toolchain so it's impossible to use right now