[JS IR] Re-export all JS-exports from main module in multi-module mode

Add an implicit transitive re-export through
main module for all other module's JS-exports.

js/js.translator/testData/box/multiModule/exportFromModules.kt

@@ -0,0 +1,54 @@
+// DONT_TARGET_EXACT_BACKEND: JS
+// KJS_WITH_FULL_RUNTIME
+
+// MODULE: ModuleA1
+// FILE: modulea1.kt
+package demoPackage.a1
+
+@JsExport
+data class ModuleA1Class(private val string: String = "A1") {
+    override fun toString(): String = string
+}
+
+// MODULE: ModuleA2(ModuleA1)
+// FILE: modulea2.kt
+package demoPackage.a2
+
+import demoPackage.a1.ModuleA1Class
+
+@JsExport
+fun moduleA2Function() = ModuleA1Class("A2")
+
+// MODULE: ModuleB
+// FILE: moduleb.kt
+package demoPackage.b
+
+@JsExport
+fun moduleBFunction() = "B"
+
+// MODULE: main(ModuleA2, ModuleB)
+// MODULE_KIND: COMMON_JS
+// FILE: main.kt
+
+package mainPackage
+
+import demoPackage.*
+
+external interface JsResult {
+    val moduleA1: String
+    val moduleA2: String
+    val moduleB: String
+}
+
+@JsModule("lib")
+external fun jsBox(): JsResult
+
+fun box(): String {
+    assertEquals(demoPackage.b.moduleBFunction(), "B")
+
+    val res = jsBox()
+    assertEquals(res.moduleA1, "A1")
+    assertEquals(res.moduleA2, "A2")
+    assertEquals(res.moduleB, "B")
+    return "OK"
+}