`AddLocalChild(LocalComponent*)` is deprecated.
It was replaced by:
`AddLocalChild(LocalComponentFactory)`, which is a type alias for a
lambda that returns a `std::unique_ptr<LocalComponentImpl>`.
This change addresses problems that arised due to object lifetime
management of the components, and allows RealmBuilder to model the
component lifecycle of local components in a way that's more consistent
with other components.
The RealmBuilder-built `Realm` now owns the lifetime of the local
components, instead of the client, and those objects are valid until
the `Realm` is destroyed.
Bug: fxbug.dev/109804
e43616416f