Configure custom Kotlin Serialization converter

Prior to this commit, `HttpMessageConverters` would consider the Kotlin
Serialization JSON converter as an alternative to the Jackson variant.
As seen in related issues, this converter is more commonly used for
annotated classes specifically and applications often rely on Jackson
acting as a fallback for types not supported by Kotlin Serialization.

This commit enables applications to configure such a converter on
`HttpMessageConverters` and order it ahead of of the JSON one.

Closes gh-35733

Author: bclozel