[foundation] fragment() helper function definition and handling

[toth-istvan-zoltan]

This code produces wrong result because fragment() is translated into the fragment parameter of patchDescendant by StateAccessTransform.

@Adaptive
fun tc(vararg instructions : AdaptiveInstruction) {
    T1(fragment().instructions.firstOrNullIfInstance<Test>()?.i ?: 999)
}

The basic solution would be to use the declaring fragment.

However, what does fragment() mean in this code.

@Adaptive
fun a() {
    row {
        fragment().also { println(it) }
    }
}