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/reflect/api/build.gradle

@@ -44,8 +44,7 @@ jar {
 
 task java9Jar(type: Jar) {
     classifier = "java9"
-    // TODO: enable as soon as this doesn't cause D8/DX to crash
-    // from sourceSets.java9.output
+    from sourceSets.java9.output
 }
 
 artifacts {