Spring Web handlers don't support Kotlin extensions

Hi.

while migrating from spring-boot 3.1.5 -> 3.2.0 all the Exception-handlers stopped working in our project. It turns out that functions can't be declared as kotlin extension functions anymore. Here's a code sample that works as expected for spring-boot-3.1.5 and not for spring-boot-3.2.0

```@SpringBootApplication class DemoApplication

fun main(args: Array) { runApplication(*args) }

@RestController class MyController{

@GetMapping("/test")
fun test() : String {throw CustomException()}

@ExceptionHandler(CustomException::class)
fun CustomException.handle(): ResponseEntity<Any>{
    return ResponseEntity.status(HttpStatus.I_AM_A_TEAPOT.value()).build()
}

}

class CustomException : Throwable() ```