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.

compiler/testData/cli/js/jsExtraHelp.out

@@ -1,6 +1,8 @@
 Usage: kotlinc-js <options> <source files>
 where advanced options include:
-  -Xtypedarrays              Translate primitive arrays to JS typed arrays
+  -Xtyped-arrays             Translate primitive arrays to JS typed arrays
+  -Xfriend-modules-disabled  Disable internal declaration export
+  -Xfriend-modules=<path>    Paths to friend modules
   -Xno-inline                Disable method inlining
   -Xrepeat=<count>           Repeat compilation (for performance analysis)
   -Xskip-metadata-version-check Load classes with bad metadata version anyway (incl. pre-release classes)
@@ -14,4 +16,4 @@ where advanced options include:
                              Enable coroutines or report warnings or errors on declarations and use sites of 'suspend' modifier
 
 Advanced options are non-standard and may be changed or removed without any notice.
-OK
+OK

compiler/testData/codegen/box/mangling/internal.kt

@@ -0,0 +1,37 @@
+// MODULE: lib
+// FILE: lib.kt
+
+package lib
+
+internal fun foo() = 1
+
+internal val bar = 2
+
+internal class A {
+    internal fun baz(a: Int): Int {
+        return a * 10
+    }
+
+    internal val foo = 3
+
+    internal inner class B {
+        internal fun foo() = 4
+    }
+}
+
+// MODULE: main(lib)(lib)
+// FILE: main.kt
+
+package main
+
+import lib.*
+
+fun box(): String {
+    if (foo() != 1) return "fail 1: ${foo()}"
+    if (bar != 2) return "fail 2: ${bar}"
+    val a = A()
+    if (a.baz(10) != 100) return "fail 3: ${a.baz(10)}"
+    if (a.foo != 3) return "fail 4: ${a.foo}"
+    if (a.B().foo() != 4) return "fail 5: ${a.B().foo()}"
+    return "OK"
+}