[FIR] Introduce & use SourceElementPositioningStrategies.OPERATOR

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/PositioningStrategies.kt

@@ -687,4 +687,14 @@ object PositioningStrategies {
             return DEFAULT.mark(element)
         }
     }
+
+    val OPERATOR: PositioningStrategy<KtExpression> = object : PositioningStrategy<KtExpression>() {
+        override fun mark(element: KtExpression): List<TextRange> {
+            return when (element) {
+                is KtBinaryExpression -> mark(element.operationReference)
+                is KtUnaryExpression -> mark(element.operationReference)
+                else -> super.mark(element)
+            }
+        }
+    }
 }