[JS IR] Add a test case with same names for private val

The test case checks, that KT-44728 has been already fixed

js/js.translator/testData/box/multiFile/samePrivateVals.kt

@@ -0,0 +1,22 @@
+// FILE: file1.kt
+package foo
+
+private val jsObject: dynamic = js("{str: 'File1Str'}")
+private val fileString: String = jsObject.str
+fun file1Fun() = fileString
+
+// FILE: file2.kt
+package foo
+
+private val jsObject: dynamic = js("{str: 'File2Str'}")
+private val fileString: String = jsObject.str
+fun file2Fun() = fileString
+
+// FILE: box.kt
+package foo
+
+fun box(): String {
+    assertEquals(file1Fun(), "File1Str")
+    assertEquals(file2Fun(), "File2Str")
+    return "OK"
+}