Improve precision of resume analysis on let binders

[b-studios]

In this PR I try to improve the precision of the resume analysis. In particular we want to have for

effect writer {
  fun write(n : int): ()
}

Scoped

val ignore = handler {
  fun write(n) {
    val x = resume(())
    val y = ()
    println(n);
    resume(())
  }
}

and

val ignore = handler {
  fun write(n) {
    val x = resume(())
    val y = resume(())
    println(n);
  }
}

Scoped Once

val ignore = handler {
  fun write(n) {
    val x = resume(())
    val y = ()
    println(n);
  }
}

Tail

val ignore = handler {
  fun write(n) {
    val y = ()
    println(n);
    resume(())
  }
}

@daanx I am not sure whether I am missing something for recursive defs

[b-studios]

@daanx ping :)