Add rustfmt rules to the project.

[xgreenx]

Added rustfmt rules. I used my favorite rules but we can discuss your wishes=) It requires usage of nightly rustfmt because it contains many new configurations. Formatted the whole project, so it will make ongoing PR harder(you need to fix conflicts) Added CI to check the fmt.

[xgreenx]

You can check what the code looks like and decide whether it is okay or not=) And maybe better to merge other PR first before this one.

[xgreenx]

We actually can remove it because it is very fas check(~10 seconds) =)

[xgreenx]

I think its a good thing to have a fmt standard. But then if we are diverging from the default of rustfmt, we might want to enforce that to all our repos so we don't end up having different styles across the org

Yea, if we are okay to apply rustfmt for fuel-core then better to do the same for all rust repos=)

[adlerjohn]

If this requires an org-wide change then it should have org-wide buy-in. Might be time to follow-up on https://github.com/FuelLabs/rfcs/pull/8

[leviathanbeak]

Reviewed all the config options, apart from maybe imports_granularity = "Crate/Module" I don't see much use in enforcing other ones, that is, diverging from the default values.

[Voxelot]

@adlerjohn we need to update the ci requirements on the repo to merge this pr

[Voxelot]

@xgreenx can you also update CONTRIBUTING.md with the updated instructions for running the nightly formatter?