* [code quality] merge style and quality targets

Any reason why we don't run `flake8` in `make style`? I find myself needing to run `make style` and `make quality` all the time, but I need the latter just for the last 2 checks. Since we have no control over the source code why bother with separating checking and fixing - let's just have one target that fixes and then performs the remaining checks, as we know the first two have been done already.

This PR suggests to merge the 2 targets into one efficient target.

I will edit the docs if this change resonates with the team.

* move checks into style, re-use target

* better name

* add fixup target

* document new target