Add support for `BeanPostProcessor` defined in Kotlin `companion object`

[sdeleuze]

Related to #32929, It looks like there is no proper way yet to declare a BeanPostProcessor in Kotlin since:

• @Bean on a member function does not translate to a static method
• companion object translates to a nested static final class Companion + related static final Companion Companion field.
• companion object + @JvmStatic translates to a duplicated bean error since the BeanPostProcessor method is exposed both in the `Companion nested class (non static method) and configuration class (static method).

Spring should support the companion object + @JvmStatic use case.