Relocate `ConfigurationPropertiesReflectionHintsProcessor` and refactor
it to be a general purpose `BindableRuntimeHintsRegistrar`.
Prior to this commit, `ConfigurationPropertiesReflectionHintsProcessor`
was used to declare binding hints for classes that were bound, but
might be `@ConfigurationProperties`. By moving and renaming the class,
it's now better aligned to the way it's used.
Support for `@NestedConfigurationProperties` has been implemented by
adding a `@Nestable` meta-annotation. This allow us to create the
appropriate hints, without the `Binder` needing to be directly aware of
the `@NestedConfigurationProperties` annotation.
Closes gh-32815
ea094ddba6