Replace the `ApplicationContextAotInitializer` class with an
`AotApplicationContextInitializer` interface so that its use can be
detected using a simple `instanceof` check. The existing functionality
has been moved to a factory method on the interface allowing:
`new ApplicationContextAotInitializer()
.initialize(context, names);`
To now be written as:
`AotApplicationContextInitializer.forInitializerClasses(names)
.initialize(context);`
See gh-29157
ac13d26077