No need for FunctionalSpringApplication anymore

[sdeleuze]

FunctionalSpringApplication does not seems to be compatible by design with the new AOT engine since it is doing a lot of infra initialization in ContextFunctionCatalogInitializer which is only invoked at runtime. What is done in ContextFunctionCatalogInitializer is hidden behind instance supplier so we can't really do something about it at buildtime.

Since the new AOT engine already generates an optimized ApplicationContextInitializer from the annotation programming model, I don't think FunctionalSpringApplication is still needed, the application can be developed as usual and will use ApplicationContextInitializer automatically at runtime.