class InstanceLocatorInit

Implements a locator for an OpenThread Instance object.

The `InstanceLocatorInit` is similar to `InstanceLocator` but provides a default constructor (instead of a

parameterized one) and allows an inheriting class to initialize the object (set the OpenThread Instance) post

constructor call using the `Init()` method. This class is intended for types that require a default constructor and

cannot use a parameterized one. (e.g., `Neighbor`/`Child`/`Router` classes which are used as a C array element type

in`ChildTable`/`RouterTable`).

The inheriting class from `InstanceLocatorInit` should ensure that object is properly initialized after the object

is created and more importantly that it is re-initialized when/if it is cleared or reset.