[Native][tests] Initial support for CExport in the new test infra

Very trivial implementation of CExport test infrastructure based on
work from LLDB tests and ObjCExport tests.

native/native.tests/testData/CExport/smoke0/main.c

@@ -0,0 +1,7 @@
+#include "smoke0_api.h"
+
+int main() {
+    if (foo() != 42) {
+        return -1;
+    }
+}

native/native.tests/testData/CExport/smoke0/main.kt

@@ -0,0 +1,8 @@
+@file:OptIn(kotlin.experimental.ExperimentalNativeApi::class)
+
+import kotlin.native.CName
+
+@CName("foo")
+fun foo(): Int {
+    return 42
+}