Process '$' correctly in "Convert concatenation to template"

So #KT-12226 Fixed

idea/src/org/jetbrains/kotlin/idea/intentions/ConvertToStringTemplateIntention.kt

@@ -86,9 +86,10 @@ open class ConvertToStringTemplateIntention : SelfTargetingOffsetIndependentInte
 
                     if (KotlinBuiltIns.isChar(type)) {
                         val value = expressionText.removePrefix("'").removeSuffix("'")
-                        return when (value) { // escape double quote and unescape single one
+                        return when (value) { // escape double quote and unescape single one and $
                             "\"" -> "\\\""
                             "\\'" -> "'"
+                            "$" -> if (forceBraces) "\\$" else "$"
                             else -> value
                         }
                     }

idea/testData/intentions/convertToStringTemplate/dollarSignChar.kt

@@ -0,0 +1,3 @@
+fun test(): String {
+    return "" + '$' + "foo" + '$' + "bar" + '$'<caret>
+}

idea/testData/intentions/convertToStringTemplate/dollarSignChar.kt.after

@@ -0,0 +1,3 @@
+fun test(): String {
+    return "\$foo\$bar$"<caret>
+}

idea/tests/org/jetbrains/kotlin/idea/intentions/IntentionTestGenerated.java

@@ -6768,6 +6768,12 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
             doTest(fileName);
         }
 
+        @TestMetadata("dollarSignChar.kt")
+        public void testDollarSignChar() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/convertToStringTemplate/dollarSignChar.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("endOfLineComment.kt")
         public void testEndOfLineComment() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/convertToStringTemplate/endOfLineComment.kt");