Missing replacement for ServiceLocator.postConstruct(Object)

Attempting to upgrade from Jersey 2.25.1 to 2.27, I am unable to convert the code:

```java
public T provide()
{
T object = supplier.get();
ServiceLocator locator = locatorReference.get();
locator.inject(object);
locator.postConstruct(object);
return object;
}
```

As `InjectionManager` does not have a `postConstruct(Object)` method and `AbstractHk2InjectionManager.inject(Object)` does not call `getServiceLocator().postConstruct(injectMe)`.

I believe there should be an `InjectionManager.postConstruct(Object)` method as the `createAndInitialize(Class)` method is documented as doing post-construction, there is an `InjectionManager.preDestroy(Object)` method, and it is conceivable the caller could want to mutate the object between injection and post-construction.

Start by comparing the ServiceLocator.postConstruct(Object) usage with InjectionManager.inject(Object), createAndInitialize(Class), and preDestroy(Object). Check AbstractHk2InjectionManager.inject(Object) and the existing InjectionManager API to determine the intended lifecycle behavior. Done means callers can perform injection and post-construction separately without relying on the removed ServiceLocator method.

Written by the indexing model from the issue text.