JS: create new common directory for all generated tests, migrate several tests there

js/js.translator/testData/box/inline/inlineSimpleAssignment.kt

@@ -0,0 +1,17 @@
+package foo
+
+// CHECK_NOT_CALLED: sum
+
+inline fun sum(a: Int, b: Int): Int {
+    return a + b
+}
+
+fun box(): String {
+    val sum3 = sum(1, 2)
+    assertEquals(3, sum3)
+
+    val sum6 = sum(sum3, 3)
+    assertEquals(6, sum6)
+
+    return "OK"
+}