[KAPT] Improve stub formatting; check raw stubs in tests

Merge-request: KT-MR-14244
Merged-by: Pavel Mikhailovskii <Pavel.Mikhailovskii@jetbrains.com>

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/Kapt3IT.kt

@@ -20,6 +20,7 @@ import org.gradle.api.JavaVersion
 import org.gradle.api.logging.LogLevel
 import org.gradle.testkit.runner.BuildResult
 import org.gradle.util.GradleVersion
+import org.jetbrains.kotlin.gradle.dsl.KotlinVersion
 import org.jetbrains.kotlin.gradle.tasks.USING_JVM_INCREMENTAL_COMPILATION_MESSAGE
 import org.jetbrains.kotlin.gradle.testbase.*
 import org.jetbrains.kotlin.gradle.testbase.project as testBaseProject
@@ -717,7 +718,12 @@ open class Kapt3IT : Kapt3BaseIT() {
 
             buildAndFail("build") {
                 val actual = getErrorMessages()
-                assertEquals(expected = genJavaErrorString(7, 19), actual = actual)
+                assertEquals(
+                    expected = genJavaErrorString(
+                        7,
+                        if (buildOptions.languageVersion?.startsWith("2") ?: (KotlinVersion.DEFAULT >= KotlinVersion.KOTLIN_2_0)) 18 else 19
+                    ),
+                    actual = actual)
             }
 
             buildGradle.modify {