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

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

@@ -0,0 +1,35 @@
+// MODULE: lib
+// FILE: lib.kt
+package lib
+
+var log = ""
+
+object O {
+    init {
+        log += "O.init;"
+    }
+
+    fun result() = "OK"
+}
+
+fun getResult(): String {
+    log += "before;"
+    val result = O.result()
+    log += "after;"
+    return result
+}
+
+// MODULE: main(lib)
+// FILE: main.kt
+package main
+
+import lib.*
+
+fun box(): String {
+    val result = getResult()
+    if (result != "OK") return "fail: unexpected result: $result"
+
+    if (log != "before;O.init;after;") return "fail: wrong evaluation order: $log"
+
+    return "OK"
+}