feat: expose task interface

[metcoder95]

• chore: split worker pool and task queue implementation
• refactor: remove leftovers

[metcoder95]

I'm trying to decouple the Task Queue and Worker Pool implementation so they can grow independently, mostly aiming for enable the work for #536 and do it progressively; I'd target the new balancer work directly to next as safe bet

[RafaelGSS]

Is it semver-major?

[metcoder95]

Don't think so, wasn't exported before, but if we want to be careful, we can do so

[metcoder95]

Just wanted to verify if is true that we did not expose these types, and indeed we don't.
The only form to have access to them was through

import type { Task } from 'piscina/dist/types';

Which is not officially supported, instead to access the same types they can do:

import type { PiscinaTask } from 'piscina';

[metcoder95]

I'll be merging the PR, if there's extra feedback, feel free to add it here and I'll address it in further PR