Provide a bean instance descriptor API

[snicoll]

Introspecting a type at build-time allows us to detect things that we typically do at runtime:

• Executable to use.
• Injection points to honor (typically @Autowired).
• Property values to inject, as defined on the BeanDefinition.
• Initialization and destruction callback

Offering an API that uses the same algorithm as a traditional runtime is important to keep the behavior consistent. This enhancement is further refined as follows:

• Revisit AOT constructor and factory method resolution #27920
• Implement an AOT equivalent of AutowiredAnnotationBeanPostProcessor #27921

[snicoll]

We've refactored things so that creating such a unified context is necessary. Rather, each post processor is free to express that it wants to contribute to the bean instance. This makes for a much more flexible setup.