Port break & continue to all backends

[jiribenes]

Motivation

We can port the new user-defined break and continue into all backends.
Resolves #314

Questions

• Can this break some benchmarks we use? => It would be nice to benchmark this before merging.
• Relates to Share standard library code between backends #309: can we share this and similar code among backends without needing to copy it into every backend separately?
• Do we even want this change? Is this a design we're happy with?

[b-studios]

I am a big fan of this, since it shows that effects cannot only be used the high-level but also for very low-level things like jumps.

Can this break some benchmarks we use? => It would be nice to benchmark this before merging.

Breaks running the benchmarks => That's a severe problem (we should have CI for this!)
Breaks performance => I don't care (then we should fix the performance to support these kinds of programs)

can we share this

Yes! We need a solution for this... ASAP

Do we even want this change? Is this a design we're happy with?

I'd say just merge and redesign later ;) Things to concider:

• break with a value (requires Control[T])
• how to break out of nested loops

[b-studios]

@marzipankaiser @phischu could you briefly check whether this breaks the benchmarks?

[phischu]

Breaks neither build nor performance for the benchmarks using the ml backend