JS: support internal visibility from friend modules

Friend modules should be provided using the -Xfriend-modules flag
in the same format as -libraries. No manual configuration required for
JPS, Gradle and Maven plugins.

Friend modules could be switched off using the -Xfriend-modules-disabled
flag. Doing that will
  * prevent internal declarations from being exported,
  * values provided by -Xfriend-modules ignored,
  * raise a compilation error on attemps to use internal declarations from other modules

Fixes #KT-15135 and #KT-16568.

core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/ModuleDescriptorImpl.kt

@@ -97,6 +97,10 @@ class ModuleDescriptorImpl @JvmOverloads constructor(
         setDependencies(ModuleDependenciesImpl(descriptors, emptySet()))
     }
 
+    fun setDependencies(descriptors: List<ModuleDescriptorImpl>, friends: Set<ModuleDescriptorImpl>) {
+        setDependencies(ModuleDependenciesImpl(descriptors, friends))
+    }
+
     override fun shouldSeeInternalsOf(targetModule: ModuleDescriptor): Boolean {
         return this == targetModule || targetModule in dependencies!!.modulesWhoseInternalsAreVisible
     }