UNUSED_VARIABLE is now reported only for last entry of destructuring declaration (if applicable) #KT-14221 Fixed

compiler/testData/diagnostics/tests/UnusedInDestructuring.kt

@@ -0,0 +1,9 @@
+data class D(val x: Int, val y: Int, val z: Int)
+fun foo(): Int {
+    val (x, y, z) = D(1, 2, 3)
+    return y + z // x is not used, but we cannot do anything with it
+}
+fun bar(): Int {
+    val (x, y, <!UNUSED_VARIABLE!>z<!>) = D(1, 2, 3)
+    return y + x // z is not used
+}