Add tests for enums interop with Java efficient collections

Author: anatoliykmetyuk

tests/run/enum-efficient-collections.check

@@ -0,0 +1,6 @@
+MONDAY
+TUESDAY
+SATURDAY
+WEDNESDAY
+workday
+weekend

tests/run/enum-efficient-collections.scala

@@ -0,0 +1,16 @@
+enum Day extends java.lang.Enum[Day] {
+  case MONDAY, TUESDAY, SATURDAY, WEDNESDAY
+}
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    val allDays = java.util.EnumSet.allOf(classOf[Day])
+    val dayMap = new java.util.EnumMap[Day, String](classOf[Day])
+    dayMap.put(Day.MONDAY, "workday")
+    dayMap.put(Day.SATURDAY, "weekend")
+
+    allDays.toArray.foreach(println)
+    println(dayMap.get(Day.MONDAY))
+    println(dayMap.get(Day.SATURDAY))
+  }
+}