[kotlin] Add integration test for query params (OpenAPITools#22588)

This is a test for a regression from OpenAPITools#22512 where param values
were written as a list.

Author: pkubowicz

samples/client/petstore/kotlin-jvm-spring-3-restclient/build.gradle

@@ -65,6 +65,7 @@ dependencies {
     implementation "com.fasterxml.jackson.module:jackson-module-kotlin:2.20.0"
     implementation "com.fasterxml.jackson.datatype:jackson-datatype-jsr310:2.20.0"
     implementation "org.springframework.boot:spring-boot-starter-web:$spring_boot_version"
+    testImplementation "org.springframework.boot:spring-boot-test:$spring_boot_version"
     testImplementation "io.kotlintest:kotlintest-runner-junit5:3.4.2"
     testImplementation "org.springframework.boot:spring-boot-test:$spring_boot_version"
 }