Native: add tests for ExperimentalForeignApi on cinterop declarations

Add tests checking that all (top-level) declarations generated by
cinterop now have ExperimentalForeignApi annotation.

^KT-58362

native/native.tests/tests/org/jetbrains/kotlin/generators/tests/GenerateNativeTests.kt

@@ -168,6 +168,12 @@ fun main() {
             ) {
                 model("CInterop/frameworkIncludeCategories/cases", pattern = "^([^_](.+))$", recursive = false)
             }
+
+            testClass<AbstractNativeCInteropExperimentalTest>(
+                suiteTestClassName = "CInteropExperimentalTestGenerated"
+            ) {
+                model("CInterop/experimental/cases", pattern = "^([^_](.+))$", recursive = false)
+            }
         }
 
         // ObjCExport tests.

native/native.tests/tests/org/jetbrains/kotlin/konan/blackboxtest/AbstractNativeCInteropTest.kt

@@ -43,6 +43,18 @@ abstract class AbstractNativeCInteropIncludeCategoriesTest : AbstractNativeCInte
         get() = "dependency.def"
 }
 
+// This test checks that cinterop-generated declarations have an experimental annotation.
+abstract class AbstractNativeCInteropExperimentalTest : AbstractNativeCInteropTest() {
+    override val fmodules: Boolean
+        get() = false
+
+    override val defFileName: String
+        get() = "dependency.def"
+
+    override val ignoreExperimentalForeignApi: Boolean
+        get() = false
+}
+
 @Tag("cinterop")
 abstract class AbstractNativeCInteropTest : AbstractNativeCInteropBaseTest() {
     abstract val fmodules: Boolean