Delimited Continuations: Implement `abort#` to avoid copying the continuation

Summary

The delimited continuation primops can be used to implement an exception mechanism similar to raiseIO# and catch#. However, it is presently much more costly to do so, because the equivalent of catch# (E[raiseIO# exc]) handle (which is roughly prompt# exc_prompt_tag (E[control0# exc_prompt_tag (\_k -> handle exc)])) will copy the entire stack frame E even though the continuation k is always discarded.

I suggest we provide a primop abort# :: PromptTag# a -> a -> State# RealWorld -> (# State# RealWorld, b #) as proposed by @lexi.lambda in #24165 (closed). The semantics of abort# tag e s is that of control0# tag (\_k -> e) s, but abort# can be implemented without copying the stack.

Bonus: implement a custom rewrite rule that rewrites control0 tag (\_k -> e) to prompt# tag e when _k is dead, so that this optimisation is done automatically by GHC.