JS: optimize destructuring declaration when possible

See KT-8285

js/js.translator/testData/box/expression/evaluationOrder/singleComponentDestructuring.kt

@@ -0,0 +1,20 @@
+// EXPECTED_REACHABLE_NODES: 1029
+// CHECK_VARS_COUNT: function=test count=2
+var log = ""
+
+fun test() {
+    val (a, _) = idAndLog(Pair(idAndLog(1), idAndLog(2)))
+    val (_, b) = idAndLog(Pair(idAndLog(3), idAndLog(4)))
+    log += "result:$a,$b;"
+}
+
+fun <T> idAndLog(x: T): T {
+    log += "$x;"
+    return x
+}
+
+fun box(): String {
+    test()
+    if (log != "1;2;(1, 2);3;4;(3, 4);result:1,4;") return "fail: $log"
+    return "OK"
+}