[kotlin-spring][server] Feat: Add Spring Declarative HTTP Interface support for easy client instantiation

[Picazsoo]

This implements the functionality proposed in issue 22286. (fixes #22286)
It adds a new library option to kotlin-spring generator called spring-declarative-http-interface, which allows for generation of Spring Declarative Http Interfaces for simple instantiations of clients that is available since Spring Boot 3.

I implemented ability to switch between ResponseEntity<SomeClassType> wrapped method return types or just plain SomeClassType and support for both reactive and non-reactive options.

For reactive options I implemented support for both kotlin-native coroutine approach (with the exception of not returning Flow for collections/arrays as Flow is not supported by spring declarative interfaces) as well as reactor approach with responses wrapped in Mono or Flux.

PR checklist

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• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
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I will also dare to tag members of the java-spring technical committee as this is mostly about the Spring aspect and I think the language is not as important - tagging @cachescrubber @welshm @MelleD @atextor @manedev79 @javisst @borsch @banlevente @Zomzog @martin-mfg