Add variant of builder interface where [metas] are *required*

[dlurton]

It's far too easy to forget to specify meta information when working with the generated builders. We should generate a second variation of this interface where the metas argument is required on all of the builder functions. Usage might go something like:

val ast = ToyLang.buildWithMetas {
    plus(
        lit(value = ionInt(1), metas = leftMetas),
        lit(value = ionInt(2), metas = rightMetas),
        metas = operatorMetas
    )
}