Structural based fx DSL

[raulraja]

We can leverage compiler plugins to automatically rewrite imperative flows that use Kind<F, A>.bind() into rewrites that are simply flatMap based. This will free us from the stack labels machinery which currently uses reflection, ties us to the JVM and it's slow.

An implementation may do the following:

• Find all declarations of fx blocks
• Digg into the function ordered KtCallExpression and find all suspend calls that use !
• If there are dependencies between the order of operations Rewrite the function body so each ordered ! it translates into a flatMap chain where the remaining expressions below are nested ending in a final map.

fx {
  val a = !fa
  val c = !fb(a)
  c + 1
}

becomes:

fa.flatMap { a -> 
  fb(a) 
}.map { c ->
  c + 1
}

This is similar as to how scala for comprehensions work and it would free us from being dependent on suspension and in general the coroutine limitations around fx