Remove `!#[deny(warnings)]` to improve DEX

[segfault-magnet]

!#[deny(warnings)] impedes quick prototyping, forcing all code to be without warnings for it to compile.

Also, it prevents Clippy from giving suggestions when dependencies fail to compile due to warnings.

Find a way of removing this, turning it into a CI step, but make sure that cargo make in the CI doesn't pass if any warnings are left.

[Dentosal]

We already seem to do this in our ci, so the lints in code can just be removed

https://github.com/FuelLabs/fuel-core/blob/e940d1dad4c186f7cd70547d17b0ecb087e1e0e4/.github/workflows/ci.yml#L21

[xgreenx]

The -D warnings doesn't work in the case of cargo make, it is why we've added !#[deny(warnings)]

[Dentosal]

Right, we have to add that to the Makefile.toml as well. Implemented in https://github.com/FuelLabs/fuel-core/pull/1508

[Dentosal]

One solution might be to have ci feature, and then have #[cfg_attr(feature = "ci", deny(warnings)]. Then just add --feature ci for CI checks.