Build java9 modular artifacts under 'modular' classifier

Provide additional modular artifacts as a workaround for KT-21266

Update module-info declarations:
  - add new packages
  - add exports and opens for internal PlatformImplementations
  - remove exports of kotlin.coroutines.experimental.*

#KT-27919 Fixed

libraries/stdlib/jdk7/java9/module-info.java

@@ -2,4 +2,7 @@ module kotlin.stdlib.jdk7 {
     requires transitive kotlin.stdlib;
 
     exports kotlin.jdk7;
+
+    exports kotlin.internal.jdk7 to kotlin.stdlib.jdk8;
+    opens kotlin.internal.jdk7 to kotlin.stdlib;
 }