Provide a more declarative way to implement components

[holgerbrandl]

To create a custom component, currently, the user has to

val c = object : Component(){
    override fun process() = sequence { 
        hold(1)
    }
}

But it would be super-cool if she could just do something like

val c = object : Component(){
    hold(1)
}

However, it seems impossible to implement this feature because the underlying building would require multiple receivers (SeqeneceScope and this@Component) for functioning. This is not yet possible with kotlin, so this ticket is blocked by https://youtrack.jetbrains.com/issue/KT-10468.