KT-2752: add checkers for inconsistent usage of JsName

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

@@ -1,3 +1,4 @@
+// FILE: foo.kt
 package foo
 
 fun bar(x: Int) = x
@@ -6,4 +7,9 @@ fun box(): Boolean {
     assertEquals(23, bar(23))
     assertEquals(42, foo.bar.x)
     return true
-}
+}
+
+// FILE: foobar.kt
+package foo.bar
+
+val x = 42

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

@@ -1,3 +1,4 @@
+// FILE: foo.kt
 package foo
 
 private fun bar() = 23
@@ -10,4 +11,9 @@ fun box(): Boolean {
     assertEquals(32, foo.bar.x)
 
     return true
-}
+}
+
+// FILE: foobar.kt
+package foo.bar
+
+val x = 32

js/js.translator/testData/multiFile/cases/packageAndMangledMethodDoNotClash/foobar.kt

@@ -1,3 +0,0 @@
-package foo.bar
-
-val x = 42

js/js.translator/testData/multiFile/cases/packageAndPrivateDeclarationDoNotClash/foobar.kt

@@ -1,3 +0,0 @@
-package foo.bar
-
-val x = 32