Reduce amount of dependencies

[dnaka91]

Reduce the amount of dependencies used by changing from futures to futures-util and removing enum_dispatch as it's only used for one single enum.

A naive comparison with cargo tree --all-features | wc -l:
Before: 289
After: 263

Pull request checklist:

• CHANGELOG.md was updated, if applicable

[RAnders00]

Would appreciate if you could add enum_dispatch back. I don't like unrolling the boilerplate. event_loop.rs is already too long and complex anways, it really doesnt need the extra boilerplate.

[dnaka91]

Sure no problem, I think the biggest reduction comes actually from futures-util as most the transitive dependencies of enum_disptach are already on the dependency graph due to other deps.

[RAnders00]

Thank you very much!