JS: refactor flat declaration generator. Add more tests on inter-module dependencies

js/js.translator/testData/box/crossModuleRef/callableObjectRef.kt

@@ -0,0 +1,25 @@
+// MODULE: lib
+// FILE: lib.kt
+package lib
+
+object O {
+    operator fun invoke() = "OK"
+}
+
+inline fun callO() = O()
+
+// MODULE: main(lib)
+// FILE: main.kt
+package main
+
+import lib.*
+
+fun box(): String {
+    val a = O()
+    if (a != "OK") return "fail: simple: $a"
+
+    val b = callO()
+    if (b != "OK") return "fail: inline: $a"
+
+    return "OK"
+}