KT-50033 Add missing public API packages to module-info and setup a test

The test checks that new packages are not accidentally non-exported,
so each new stdlib package must be either exported or specified in that
test's expected non-exported package list.

libraries/stdlib/jvm/java9/module-info.java

@@ -8,6 +8,7 @@ module kotlin.stdlib {
     exports kotlin.concurrent;
     exports kotlin.contracts;
     exports kotlin.coroutines;
+    exports kotlin.coroutines.cancellation;
     exports kotlin.coroutines.intrinsics;
     exports kotlin.coroutines.jvm.internal;
     exports kotlin.io;