Add EvolComplexity task

[davidberenstein1957]

Description

Implements EvolComplexity as a wrapper around EvolInstruct but with limited template options.

Closes #392

[alvarobartt]

Didn't review yet, but I'd place evol_complexity under EvolInstruct since it's based on it, rather than having it in a separate module, we can work on the imports later on i.e. from distilabel.tasks import EvolComplexity, EvolInstruct

[davidberenstein1957]

@alvarobartt, I thought it was more structured when searching for tasks to have them in separate folders but I'll change the structure a bit.

[davidberenstein1957]

@alvarobartt feel free to review

[alvarobartt]

Hi here! Some comments, but besides that I meant to nest the EvolComplexity within a separate directory as evol_instruct/complexity/base.py or something similar, to me is clearer, WDYT?

[alvarobartt]

I wouldn't mix the tests here, i.e. EvolInstruct separately

[davidberenstein1957]

I think we'll create a lot of code/test-duplication for inherently testing the same things so I think it is better to keep it like this.

[alvarobartt]

I was thinking that as EvolComplexity is just inheriting from EvolInstruct and modifying the mutation_templates, only that should be tested. Because the rest of it is just a duplication from EvolInstruct, so there's no need to run the same tests twice, so a check on the mutation_templates should be enough IMO. That would also help on keeping everything more organized IMO.