Merge #235

235: Refactorise the settings r=curquiza a=irevoire

This PR unifies the two types `Settings`. 
It also gets rids of the `IntoVecString` in favor of a simpler `IntoIterator<Item = AsRef<str>>`, which is more versatile and common in rust.

Co-authored-by: Irevoire <[email protected]>

Author: bors[bot]