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/jdk8/java9/module-info.java

@@ -1,7 +1,10 @@
 module kotlin.stdlib.jdk8 {
     requires transitive kotlin.stdlib;
+    requires kotlin.stdlib.jdk7;
 
     exports kotlin.collections.jdk8;
     exports kotlin.streams.jdk8;
     exports kotlin.text.jdk8;
+
+    opens kotlin.internal.jdk8 to kotlin.stdlib;
 }