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/testData/CInterop/experimental/include/enum.h

@@ -0,0 +1,8 @@
+enum E1 {
+    ONE, TWO, THREE
+};
+
+enum E2 {
+    FOUR = 4,
+    EIGHT = 8
+};