Fix "Too long character literal -> string" in ILLEGAL_ESCAPE

Related to #KT-23788

idea/src/org/jetbrains/kotlin/idea/quickfix/TooLongCharLiteralToStringFix.kt

@@ -4,7 +4,6 @@ import com.intellij.codeInsight.intention.IntentionAction
 import com.intellij.openapi.editor.Editor
 import com.intellij.openapi.project.Project
 import org.jetbrains.kotlin.diagnostics.Diagnostic
-import org.jetbrains.kotlin.diagnostics.Errors
 import org.jetbrains.kotlin.psi.KtConstantExpression
 import org.jetbrains.kotlin.psi.KtFile
 import org.jetbrains.kotlin.psi.KtPsiFactory
@@ -36,6 +35,7 @@ class TooLongCharLiteralToStringFix(
         override fun createAction(diagnostic: Diagnostic): IntentionAction? {
             val element = diagnostic.psiElement as? KtConstantExpression ?: return null
             if (element.text == "'\\'") return null
+            if (element.text.startsWith("\"")) return null
             return TooLongCharLiteralToStringFix(element = element)
         }
     }

idea/testData/quickfix/tooLongCharLiteralToString/startWithBackslashInString.kt

@@ -0,0 +1,8 @@
+// "Convert too long character literal to string" "false"
+// ACTION: Introduce local variable
+// ACTION: To raw string literal
+// ERROR: Illegal escape: '\ '
+
+fun foo() {
+    "\ <caret>"
+}

idea/tests/org/jetbrains/kotlin/idea/quickfix/QuickFixTestGenerated.java

@@ -10525,6 +10525,11 @@ public class QuickFixTestGenerated extends AbstractQuickFixTest {
         public void testStartWithBackslash() throws Exception {
             runTest("idea/testData/quickfix/tooLongCharLiteralToString/startWithBackslash.kt");
         }
+
+        @TestMetadata("startWithBackslashInString.kt")
+        public void testStartWithBackslashInString() throws Exception {
+            runTest("idea/testData/quickfix/tooLongCharLiteralToString/startWithBackslashInString.kt");
+        }
     }
 
     @TestMetadata("idea/testData/quickfix/typeAddition")