Code Insight: "Generate toString" action

#KT-10309 Fixed

idea/testData/codeInsight/generate/toString/singleTemplate/singleVar.kt.after

@@ -0,0 +1,10 @@
+// GENERATOR: SINGLE_TEMPLATE
+class A(val n: Int) {
+    fun foo() {
+
+    }
+
+    <caret>override fun toString(): String{
+        return "A(n=$n)"
+    }
+}