Spring SPR-15755: Introduce Kotlin functional bean registration DSL

As a follow-up of the ApplicationContext Kotlin extensions, close to the Kotlin functional WebFlux DSL and similar to the Groovy bean configuration DSL (but very different in term of implementation since no internal XML-based application context is involved), this commit is about introducing a lightweight Kotlin DSL for functional bean registration.

It allows declaring beans as following:

beans {
    bean<Foo>()
    profile("bar") {
        bean<Bar>("bar")
    }
    environment({it.activeProfiles.contains("baz")}) {
        bean { Baz(it.ref()) }
        bean { Baz(it.ref("bar")) }
    }
}

Advantages compared to Regular ApplicationContext API are: - No exposure of low-level ApplicationContext API - Focused DSL easier to read, but also easier to write with a fewer entries in the auto-complete - Declarative syntax instead of functions with verbs like registerBeans while still allowing programmatic registration of beans with if expressions or for loops - Such DSL is idiomatic in Kotlin - No need to have an ApplicationContext instance to write how you register your beans since beans { } DSL is conceptually a Consumer<ApplicationContext>

This DSL effectively replaces ApplicationContext Kotlin extensions as the recommended way to register beans in a functional way with Kotlin.