Introduce "Unused unary operator" inspection

#KT-12073 Fixed

idea/testData/inspectionsLocal/unusedUnaryOperator/userOperator.kt

@@ -0,0 +1,11 @@
+// PROBLEM: none
+data class Point(val x: Int)
+
+operator fun Point.plus(other: Point) = Point(this.x + other.x)
+
+operator fun Point.unaryMinus() = Point(-x)
+
+fun test() {
+    val p = Point(1) + Point(2)
+    <caret>-Point(3)
+}