UTBot generates Java tests inside `.kt` file for Kotlin code

[tyuldashev]

Description

When user starts test generation for Kotlin code UTBot creates .kt file and put there Java code which obviously cannot be compiled.

To Reproduce

Steps to reproduce the behavior:

1. Open UTBot Java project
2. In UTBot settings set "Generated test language" = "Kotlin"
3. Invoke test generation for org/utbot/examples/codegen/FileWithTopLevelFunctions.kt

Expected behavior

Functional Kotlin tests are generated.

Actual behavior

FileWithTopLevelFunctionsKtTest.kt created with Java code which cannot be executed.

Visual proofs (screenshots, logs, images)