[Engine] expose an `updated` callback for services about lwc

[kevinv11n]

fyi @caridy @yungcheng

[caridy]

@kevinv11n is this still something that we need to consider? or can this be closed?

[kevinv11n]

We’ll move @wire to a real decorator in the future which makes the service usable in other frameworks. Property descriptor hooks remain the approach which will still require a microtask to queue for when all property updates are complete.

[jbenallen]

The @wire decorator implementation will need access to the element's lifecycle callbacks, which means that its implementation will need access to privileged hooks as it has through the service hooks today. It's the same technical obstacles related to #512.