layer extension helpers

[LizAinslie]

create a LayerProperty delegate interface and a few OOTB behaviors

default behavior should be lazy. we only want to instantiate values on the scope when we need them

example usages:

// where TLayer : ApplicationLater<TLayer>
var TLayer.var1 by LayerProperty {
  // this block is TLayer.() -> TProperty
  "some variable"
}

var TLayer.someClass by LayerProperty.ServiceLoader<SomeClass> {
  // an optional setup block, running as SomeClass.() -> Unit
}

// etc

i'll add to this as i think of new OOTB behaviors i want to include and will only close the issue after that