* [bench-hist] break down in rule functions

* Extract the benchmarking Shake rules to a shake-bench package

There's some room for reusing the rules used in the historic benchmarking suite
in other projects. This change makes that a bit easier and improves the
documentation and code structure.

The new structure is:
- lib:shake-bench - a Cabal library with functions to generate Shake rules
- ghcide:bench:benchHist - the ghcide instantiation of the above Shake rules

That's not to say that shake-bench is completely decoupled from ghcide -
there are still plenty of assumptions on how the benchmarks are organized, their
outputs, etc. But with a little bit of effort, it should be easy to make
these rules more reusable

* Fix nix build

* Fix license

* hlints and redundant imports

* more hlints

* Exclude shake-bench from the stack build