Code Insight: Preserve identifier quotes in "Generate equals()/hashCode()/toString()" actions

#KT-15883 Fixed

idea/testData/codeInsight/generate/toString/singleTemplate/keepQuotes.kt

@@ -0,0 +1,3 @@
+class Example(val `in`: String, val `cl ass`: String, val `valid`: Boolean) {
+    <caret>
+}

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

@@ -0,0 +1,5 @@
+class Example(val `in`: String, val `cl ass`: String, val `valid`: Boolean) {
+    override fun toString(): String {
+        return "Example(`in`='$`in`', `cl ass`='$`cl ass`', `valid`=$`valid`)"
+    }
+}